A clinical trial “study team” is not one job — it is a division of labor between the investigational site and the trial’s sponsor (or the contract research organization, CRO, acting on the sponsor’s behalf). Each side has its own roles, its own chain of accountability, and its own regulatory basis for who is authorized to do what. Understanding how those roles fit together — who reports to whom, who is legally accountable for a given task, and where site-side responsibility ends and sponsor/CRO-side oversight begins — is foundational to how a trial actually runs day to day.
This page maps the team structure. For the detailed definition of any individual role, follow the links to that role’s own dictionary entry rather than treating this page as the primary source — it is deliberately an overview, not a replacement for the dedicated terms.
The Two Sides of a Study Team: Site and Sponsor/CRO
Every clinical trial study team splits along one basic line: who employs the person, and who they are accountable to.
- Site-based roles are employed by the investigational site itself — a hospital, academic medical center, or dedicated research site — and are responsible for the day-to-day conduct of the trial with the participants who are physically enrolled there.
- Sponsor- and CRO-based roles are employed by the trial sponsor or by a CRO acting on the sponsor’s behalf, and are responsible for overseeing site conduct across a portfolio of sites, verifying that what happens at each site matches the protocol and Good Clinical Practice (GCP).
This employer/authority split is what separates roles that look superficially similar. A Clinical Research Coordinator (CRC) and a Clinical Research Associate (CRA) both spend their time immersed in trial data and documents, but a CRC works for the site and executes study visits, while a CRA works for the sponsor/CRO and independently verifies what the site has already done.
Site-Based Roles
Principal Investigator (PI)
The Principal Investigator is the person formally accountable for the scientific, ethical, and regulatory conduct of the trial at a given site. Under FDA regulation, when an investigation is conducted by a team, the PI is “the responsible leader of the team” (21 CFR 312.3(b)) — every other site role exists under the PI’s delegated authority, documented on a delegation of authority log that records who on the team is authorized to perform which trial-related tasks and from what date.
Sub-Investigator
A sub-investigator is any other individual member of the site study team — a co-investigator, fellow, resident, or other clinician — to whom the PI has delegated specific trial-related duties, most often direct interaction with participants such as conducting study visits or assessing eligibility. FDA’s own definition, from 21 CFR 312.3(b), is intentionally broad: “‘Subinvestigator’ includes any other individual member of that team.” A sub-investigator does not carry the PI’s overall regulatory accountability for the trial, but is individually listed, alongside the PI, on the site’s FDA Form 1572 for a trial conducted under an Investigational New Drug (IND) application, and performs work under the PI’s supervision and the delegation log’s authorization.
Clinical Research Coordinator (CRC)
The Clinical Research Coordinator manages the operational, day-to-day conduct of the trial at the site: screening and consenting participants, scheduling and running study visits, entering data into case report forms, and maintaining source documents and the site’s regulatory file. A CRC works under the PI’s delegated authority and is the role a CRA’s monitoring visits most directly interact with, since the CRA’s source-data verification checks the CRC’s documentation against what was actually done.
Regulatory Coordinator
On larger sites or site networks, regulatory responsibilities are often split out from general coordination into a dedicated regulatory coordinator role. This person maintains the site regulatory binder or electronic Trial Master File (the site-level portion of the broader Trial Master File (TMF)), tracks IRB/ethics-committee submissions and continuing-review deadlines, manages protocol amendment paperwork, and keeps investigator licensure, training, and financial-disclosure documentation current. Not every site formalizes this as a separate title — on smaller sites the CRC or the PI absorbs this work directly — but the function itself exists on every trial regardless of who performs it.
Data Manager
Some sites, particularly those running large or complex trials, staff a dedicated data manager whose focus is the quality and completeness of what goes into the electronic data capture (EDC) system: resolving data queries raised by the sponsor or CRA, reconciling case report form entries against source documents, and supporting database lock activities at the end of a trial. Where a site does not staff this as a distinct role, the CRC typically performs this function alongside their other duties. This site-level function is distinct from a sponsor’s clinical data management team, which owns the EDC system, query rules, and database design across the whole trial — see the clinical research pillar for how data management fits into the broader trial lifecycle.
Sponsor- and CRO-Based Roles
Clinical Research Associate (CRA)
The Clinical Research Associate performs the monitor function defined in ICH E6: overseeing a portfolio of sites on behalf of the sponsor or CRO, verifying source data against case report forms, confirming protocol and GCP compliance, and reporting site-visit findings back to the sponsor. A CRA is not part of any single site’s team in the employment sense — the CRA’s accountability runs to the sponsor, and their job is specifically to independently check the site team’s work, not to perform it.
Clinical Trial Associate (CTA)
The Clinical Trial Associate is an entry-level, sponsor- or CRO-side administrative and project-tracking role that supports the CRA’s workload: maintaining the Trial Master File and site regulatory documents, scheduling site visits and meetings, and tracking study timelines and action items. A CTA does not independently conduct monitoring visits or exercise the CRA’s oversight authority over site conduct — the distinction mirrors the one between a CRC and a data manager on the site side: administrative/logistical support versus the role that carries independent authority.
How Team Authority Is Documented
A study team’s structure is not just informal practice — it is a set of documents an inspector or auditor can check. Two documents in particular tie people to authority:
- FDA Form 1572 (for US IND-regulated drug/biologic trials) formally lists the PI and every sub-investigator at a site, and is signed by the PI as an attestation of who is authorized to conduct the study.
- The delegation of authority log is the site-level record — maintained as part of the site’s regulatory file or TMF — of exactly which trial-related tasks each team member is authorized to perform, and from what date, based on their qualifications and training. Inspectors routinely cross-check this log against source documents to confirm that whoever performed a given task (consenting a participant, assessing an adverse event, entering data) was actually delegated the authority to do so.
Both documents exist because GCP requires that trial-related authority be traceable to a specific, qualified individual — not exercised informally by whoever happens to be available.
Typical Reporting Lines
On a single-site trial, the structure is usually straightforward: the PI leads the site team, with sub-investigators, the CRC, and (where staffed separately) the regulatory coordinator and data manager all working under the PI’s delegated authority, while the CRA (and, behind them, a CTA) monitors that site independently on behalf of the sponsor or CRO. On a multi-site trial, this same site-level structure repeats at every location, with a sponsor-side clinical operations team — including a lead CRA or clinical trial manager overseeing the whole CRA portfolio — coordinating across sites. Neither side manages the other: the PI does not supervise the CRA, and the CRA does not supervise site staff. The relationship is oversight and verification, not a single management hierarchy, which is precisely why the employer/authority distinction at the top of this page is the right way to think about study team structure, rather than a single organizational chart.
Frequently Asked Questions
Who leads a clinical trial study team?
At the site level, the Principal Investigator is the responsible leader — every other site-based role operates under the PI’s delegated authority. On the sponsor/CRO side, there is no equivalent single leader of “the” study team as a whole; sponsor-side roles (CRA, CTA, and the broader clinical operations function) oversee site conduct rather than lead it.
Is a CRA part of the site’s study team?
No. A CRA is employed by the sponsor or CRO and is accountable to them, not to the site. The CRA’s function is to independently monitor and verify the site team’s work, which is why a CRA cannot also be a site team member without compromising that independence.
Can a sub-investigator sign the informed consent form?
Whether a sub-investigator may obtain informed consent depends on whether the PI has delegated that specific task to them on the delegation of authority log, and on local IRB and institutional policy — it is not automatic just by virtue of being listed on Form 1572. This page describes team structure generally; consent-specific requirements should be confirmed against the trial’s own IRB-approved procedures.
What is the difference between a CRC and a CTA?
Both are largely administrative/coordination roles, but on opposite sides of the site/sponsor divide: a CRC is site-employed and runs the trial day to day with participants, while a CTA is sponsor- or CRO-employed and supports the CRA’s monitoring and documentation workload. Neither independently exercises the oversight authority that belongs to the PI (site side) or the CRA (sponsor side).
Does every trial staff a regulatory coordinator and a data manager as separate roles?
No. Smaller sites typically fold these functions into the CRC role rather than staffing dedicated positions. The functions themselves — regulatory document tracking and EDC data quality — exist on every trial regardless of title; only whether they are split into distinct roles varies with site size and trial complexity.
