Good Clinical Practice (GCP): ICH E6 Explained

Good Clinical Practice (GCP) is the international ethical, scientific, and quality standard for designing, conducting, recording, and reporting clinical trials that involve human participants. It is set out in the International Council for Harmonisation’s ICH E6 guideline and is incorporated, directly or by reference, into the regulatory frameworks of every major medicines regulator, including the FDA, EMA, MHRA, PMDA, and Health Canada. Compliance with GCP is not optional for regulated interventional trials — it is the baseline a sponsor, investigator, and institutional review board are expected to meet for the trial’s data to be considered reliable and its participants’ rights and safety to be considered protected.

This guide explains what GCP actually requires, who it applies to, how the standard has evolved from ICH E6(R1) through the current E6(R3) revision, how compliance is monitored and enforced, and how GCP relates to adjacent standards like GMP, GLP, and the training/certification landscape built around it.

The regulatory standard: ICH E6 and its revisions

GCP as a formal, harmonized standard originates with the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH), a body bringing together regulators and industry from the US, EU, Japan, and other participating jurisdictions. The foundational guideline, ICH E6, was first finalized in 1996. Two later revisions matter for anyone working in clinical research today:

ICH E6(R2) (2016 addendum) added emphasis on risk-based quality management, sponsor oversight of outsourced trial functions, and electronic records/essential-document handling, without restructuring the original guideline.
ICH E6(R3), the current core guideline, reached ICH Step 4 (final) on 6 January 2025. It restructures GCP around a set of principles plus annexes, sharpens the risk-based, quality-by-design approach, and explicitly addresses decentralized and pragmatic trial designs and electronic data sources that E6(R2) did not contemplate. EMA set 23 July 2025 as the effective date for the Principles and Annex 1 in the EU; FDA issued its own final E6(R3) guidance on 8 September 2025.

Because implementation dates differ by jurisdiction and by which annex applies, sponsors running multi-region trials need to track both revisions during the transition period rather than assuming a single global cutover date.

The core principles of GCP

ICH E6 sets out its requirements as a small number of core principles that everything else in the guideline operationalizes. In substance, these principles establish that:

Trials must be conducted in accordance with ethical principles that have their origin in the Declaration of Helsinki and are consistent with GCP and applicable regulatory requirements.
The anticipated benefits of a trial must justify the risks, established through a risk/benefit assessment before the trial begins and reassessed as it proceeds.
The rights, safety, and well-being of trial participants are the most important considerations and must prevail over the interests of science and society.
Available nonclinical and clinical information on the investigational product must be adequate to support the proposed trial.
Trials must be scientifically sound and described in a clear, detailed protocol.
A trial must be conducted in compliance with the protocol that has received prior IRB/IEC approval or favorable opinion.
Medical care of, and medical decisions on behalf of, participants must always be the responsibility of a qualified physician or dentist.
Everyone involved in conducting a trial must be qualified by education, training, and experience to perform their respective tasks.
Freely given informed consent must be obtained from every participant before trial participation.
All trial information must be recorded, handled, and stored in a way that permits accurate reporting, interpretation, and verification.
The confidentiality of records that could identify participants must be protected.
Investigational products must be manufactured, handled, and stored in accordance with Good Manufacturing Practice, and used in accordance with the approved protocol.
Systems with procedures to assure the quality of every aspect of the trial must be implemented.

These principles are what a sponsor’s SOPs, a site’s Trial Master File, and a monitor’s visit checklist are all, ultimately, built to demonstrate compliance with.

Who GCP applies to, and who is responsible for what

GCP assigns distinct, overlapping responsibilities rather than a single compliance owner:

Sponsors are responsible for overall trial oversight, including selecting qualified investigators, implementing quality management and risk-based monitoring, ensuring safety reporting, and maintaining oversight of any functions delegated to a contract research organization (CRO) — delegation does not transfer the sponsor’s underlying regulatory responsibility.
Investigators are responsible for the conduct of the trial at their site: protocol adherence, participant safety, accurate source documentation, obtaining informed consent, and appropriate delegation of tasks to qualified staff.
IRBs/IECs are responsible for reviewing and approving the protocol, informed consent materials, and ongoing trial conduct to protect participant rights and welfare.
CROs, where used, perform sponsor-delegated functions but operate under the sponsor’s oversight and within the sponsor’s documented quality system.

How GCP is incorporated into national and regional regulation

ICH E6 itself is a guideline, not a directly enforceable law in most jurisdictions — it becomes binding through national and regional implementation. In the United States, GCP-equivalent obligations are set out across FDA regulations including 21 CFR Parts 50 (informed consent), 54 (financial disclosure by clinical investigators), 56 (IRBs), and 312 (IND applications), with FDA’s E6(R3) guidance now incorporating the ICH text directly. In the European Union, GCP obligations are anchored in the EU Clinical Trials Regulation (EU) No 536/2014. Other ICH member and observer regulators — including the UK’s MHRA, Japan’s PMDA, and Health Canada — incorporate ICH E6 into their own clinical trial regulations and guidance in comparable ways. Medical device trials follow a related but distinct standard, ISO 14155 ("Clinical investigation of medical devices for human subjects — Good clinical practice"), rather than ICH E6, which was written for drug and biologic trials.

GCP training requirements

Regulators and funders increasingly require documented GCP training, not just GCP-consistent conduct. NIH policy (NOT-OD-16-148, effective 1 January 2017) requires all NIH-funded investigators and staff responsible for the conduct, management, or oversight of an NIH-funded clinical trial to complete GCP training, refreshed at least every three years, regardless of trial phase or intervention type. In practice, most sites and sponsors meet this through commercial or nonprofit training providers — CITI Program’s GCP course series (aligned to ICH E6, with separate tracks for drug/biologic and device trials) is one of the most widely used, and its completions are recognized under TransCelerate’s GCP Mutual Recognition Program across participating sponsor companies without separate retraining. This is distinct from the credentialing-exam route covered in our separate guide on GCP certification — GCP training documents that someone has completed a course; certification, where it exists, is a credentialing body’s exam-based credential built on top of that same underlying content.

How GCP compliance is monitored and enforced

GCP compliance is checked continuously during a trial, not just at its conclusion. Sponsors (directly or via a CRO) conduct routine monitoring visits — site initiation, interim, and close-out visits that include source data verification against case report forms. Independently, sponsors, institutions, and regulators conduct GCP audits, which differ from monitoring in scope and independence: audits are typically conducted by a party not involved in day-to-day trial conduct and assess systemic compliance rather than individual data points. Regulators including FDA (through its Bioresearch Monitoring, or BIMO, program) and EMA conduct their own GCP inspections of investigator sites, sponsors, and IRBs/IECs, with findings that can range from minor observations to trial data being disqualified or a site being barred from future regulated research.

GCP vs. GMP vs. GLP

GCP is one of several "GxP" quality standards that apply at different stages of drug and device development, and the three are easy to conflate:

GCP governs how a clinical trial is conducted in human participants — informed consent, protocol adherence, investigator responsibilities, and data integrity.
GMP (Good Manufacturing Practice; in the US, 21 CFR Parts 210/211 for drugs) governs how the investigational product itself is manufactured, tested, and released.
GLP (Good Laboratory Practice; 21 CFR Part 58 in the US) governs the conduct and documentation of nonclinical (preclinical) safety studies, before human trials begin.

See our full comparison of GCP vs. GMP for a side-by-side breakdown of how the two standards apply to the same trial simultaneously but govern entirely different activities.

GCP vs. GCP certification — a common point of confusion

“Good Clinical Practice” is the regulatory standard itself; “GCP certification” is not a single government-issued credential built on top of it. No regulator issues a universal GCP license, and no single body owns the term “certified” in this context — what exists is a patchwork of course-completion certificates and professional credentialing exams from different training and credentialing organizations, all aimed at demonstrating competency in the same underlying ICH E6 principles. If you’re specifically evaluating training or credentialing options, see our dedicated guide to GCP certification.

Frequently asked questions

Is GCP a law or a guideline?

ICH E6 itself is a harmonized guideline, not a law. It becomes enforceable through the regulations of each implementing jurisdiction — for example, FDA regulations in the US and the EU Clinical Trials Regulation in the EU — which is why the practical compliance obligations can vary slightly by region even though the underlying GCP principles are shared.

Does GCP apply to all clinical research, or only trials of regulated products?

ICH E6 GCP specifically applies to interventional clinical trials of regulated medical products (drugs, biologics, and, via the related ISO 14155 standard, devices). Purely observational studies and non-regulated research are typically governed by separate human-subjects-protection frameworks, such as the Common Rule or institutional IRB policy, rather than by ICH GCP directly — though many institutions apply GCP-consistent practices more broadly as a matter of policy.

Who needs GCP training?

Anyone with a substantive role in the conduct, management, or oversight of a clinical trial — investigators, sub-investigators, study coordinators, and often sponsor and CRO staff — is generally expected to hold current GCP training. NIH-funded trials have an explicit training mandate (NOT-OD-16-148) with a three-year refresh cycle; many institutions and sponsors apply a similar cadence as internal policy even where no external mandate applies.

What’s the difference between GCP monitoring and a GCP audit?

Monitoring is an ongoing, sponsor-directed activity (often performed by a clinical research associate) that checks individual site data and procedures against the protocol as the trial progresses. An audit is a more independent, systemic review — conducted by a party not involved in day-to-day conduct — of whether the overall quality system met GCP requirements. Regulatory inspections are a third, distinct layer, conducted by the regulator itself.

Is ICH E6(R2) still relevant now that E6(R3) exists?

Yes, during the transition period. Implementation and effective dates differ by regulator and, in some cases, by which part of the guideline (principles vs. annexes) is involved, so trials that started under E6(R2) or that operate in a jurisdiction still phasing in E6(R3) may need to document compliance against the earlier revision for some time yet. Sponsors running multi-region trials should confirm the applicable revision with each relevant regulator rather than assuming a single global cutover date.