Before a clinical trial can enroll a single participant, a sponsor or contract research organization (CRO) has to decide which investigative sites will actually run it. Site selection is the operational and regulatory due-diligence process that produces that decision: a sponsor identifies candidate sites, gathers structured information from each through a feasibility questionnaire, evaluates that information against a common set of criteria, and confirms a final site list before regulatory submissions and site initiation activities proceed.
Site selection sits between protocol finalization and site initiation in the trial lifecycle. It is distinct from patient recruitment, which happens once a site is already active and enrolling; site selection is about choosing which sites are capable of recruiting, retaining, and managing participants for a specific protocol in the first place.
Why site selection matters
Site performance is one of the largest drivers of trial timeline and cost risk. A site that cannot meet its enrollment target, lacks the specialty population the protocol requires, or lacks the staff and equipment to execute the protocol’s visit schedule creates delays that are expensive to fix mid-trial — reopening site selection later, adding sites, or extending enrollment windows all cost more than getting the initial site list right. Regulators also expect sponsors to exercise this diligence: under 21 CFR 312.53(a), a sponsor is required to select investigators “qualified by training and experience” to investigate the drug, and ICH E6(R2) Principle 2.8 states that each individual involved in conducting a trial should be qualified by education, training, and experience to perform their role. Site selection is the documented process that demonstrates a sponsor met that obligation before enrollment began.
The site selection process, step by step
- Candidate identification. The sponsor or CRO builds a longlist of potential sites, drawing on internal databases of previously used investigators, therapeutic-area key opinion leaders, site networks, investigator meetings, and (increasingly) claims or EHR-derived data on where the target patient population is actually treated.
- Feasibility questionnaire. Candidate sites receive a structured feasibility questionnaire, typically alongside a protocol synopsis or full protocol, asking about patient population, prior trial experience, staff, and infrastructure (see below). Sites return the completed questionnaire, often alongside a proposed enrollment projection.
- Desk review / data-driven screening. The sponsor or CRO scores returned questionnaires against defined criteria, often supplemented by objective data — the site’s actual enrollment history in the sponsor’s own database, EHR- or claims-based patient-count estimates, and past audit or monitoring findings — to shortlist sites for a closer look.
- Pre-study site visit (PSSV) / site selection visit (SSV). A clinical research associate or feasibility team visits (in person or remotely) the shortlisted site to verify what the questionnaire reported: physical facilities, equipment, pharmacy/investigational product storage, delegation of authority practices, and to meet the principal investigator and key staff directly.
- Selection decision. The sponsor finalizes the site list, balancing enrollment capacity against geographic and demographic diversity, competing-trial exposure, and budget. Selected sites move into contracting, IRB/ethics submission, and site initiation; sites that are not selected are typically notified and may be reconsidered for future protocols.
Once a site is selected, it proceeds to a site initiation visit — the meeting at which the site team is trained on the finalized protocol, systems, and procedures before the first participant can be enrolled — which is a separate step covered on its own page on this site.
What a feasibility questionnaire asks
Feasibility questionnaires vary by sponsor and therapeutic area, but they typically cover the same core categories:
- Patient population and access. How many patients meeting the protocol’s inclusion/exclusion criteria does the site see in a given period? Is that estimate based on a chart review or EHR query, or an unverified clinical impression? What proportion of that population would realistically be approached, consent, and remain eligible after screening?
- Investigator and staff experience. The principal investigator’s therapeutic-area and clinical-trial experience, prior protocol deviations or findings, current GCP training status, and the experience level of the coordinating and sub-investigator staff who will do most of the day-to-day protocol work.
- Infrastructure. Availability of required equipment, imaging, laboratory processing and shipping capability, investigational product storage (including any cold-chain requirements), and access to the specific procedures the protocol requires (for example, biopsy, apheresis, or a particular imaging modality).
- Competing studies. Other active or planned trials at the site — particularly in the same indication or competing for the same patient population — since a site juggling several competing protocols for the same population will split enrollment across them, reducing what any single trial can realistically expect.
- Regulatory and administrative track record. IRB/ethics committee turnaround time, contracting and budget-negotiation timelines, and prior audit or inspection history.
- Operational logistics. Site hours, staff turnover, distance/travel burden for participants, and language or interpreter capacity relevant to the target population.
A recurring theme in the clinical-operations literature on feasibility is that self-reported enrollment projections in questionnaires are frequently optimistic; sponsors increasingly weight objective, data-driven enrollment estimates (from claims data, EHR queries, or the sponsor’s own historical database of that site’s actual performance on prior protocols) more heavily than a site’s own projection.
Evaluation criteria in detail
Prior enrollment and performance history
For sites with a prior relationship to the sponsor or CRO, historical performance — actual enrollment achieved against target, time to first patient enrolled, retention/dropout rate, protocol deviation rate, and data query rate — is typically the single most predictive input into a selection decision, since it reflects demonstrated rather than projected capability. For new sites without that history, sponsors substitute proxies: publication record in the therapeutic area, prior trial participation reported through registries such as ClinicalTrials.gov, and references from other sponsors or CROs the site has worked with.
Patient population access
Access to the right patients is a prerequisite the rest of the evaluation is built on — a site can have excellent staff and infrastructure and still be unable to enroll if it does not see enough protocol-eligible patients. Sponsors typically validate a site’s stated patient volume against independent data sources rather than accepting a questionnaire estimate at face value, and increasingly weigh whether the site’s patient population reflects the diversity the protocol (or, for FDA-regulated trials, the sponsor’s diversity action plan) is targeting.
Principal investigator experience
The principal investigator’s qualifications are both a scientific-quality question and a specific regulatory requirement. Under 21 CFR 312.53(a), the sponsor must select investigators qualified by training and experience; the PI’s qualifications, licensure, and financial disclosures are formally documented on Form FDA 1572 (Statement of Investigator) for IND-regulated drug trials in the US. Evaluation typically looks at the PI’s prior experience running trials in the relevant therapeutic area or with the relevant patient population, time actually available to devote to the study given other clinical and research commitments, and history of protocol compliance on prior studies.
Site infrastructure and staff capacity
Beyond the PI, sponsors evaluate whether the site has the coordinating staff, sub-investigators, and physical/technical resources to execute the protocol’s specific procedures and visit schedule without becoming a bottleneck. A common failure mode identified in the site-feasibility literature is a site with strong PI credentials but insufficient coordinator time or turnover in coordinator staff, which in practice does much of the protocol’s day-to-day execution.
Competing-trial considerations
Sites operating in active therapeutic areas (oncology, in particular) are frequently running multiple concurrent trials that draw on the same patient population. Sponsors assess a candidate site’s current and planned trial portfolio to estimate how much of its stated patient volume is actually available to this specific protocol, since a site’s total capacity is shared, not additive, across every trial it is running.
Who makes the decision
For sponsor-run trials, a clinical operations or feasibility team typically owns the process, often with input from medical/therapeutic-area leads on scientific fit. Where a CRO is engaged, site selection is commonly delegated to the CRO’s feasibility and site-management function, operating against criteria and a final approval step the sponsor retains. Larger organizations frequently use a formal site selection committee or scorecard to make the evaluation auditable and consistent across candidate sites rather than left to individual reviewer judgment.
Documentation and audit trail
Because site selection is the mechanism by which a sponsor demonstrates compliance with 21 CFR 312.53(a) and the equivalent ICH E6 expectation, sponsors typically retain the completed feasibility questionnaire, site visit report, and the rationale for the final selection (or non-selection) decision as part of the trial master file, alongside the broader clinical data management and monitoring records the trial generates. This documentation matters during a regulatory inspection or audit, where an inspector may ask a sponsor to show why a given site was judged qualified to conduct the trial.
Frequently asked questions
What is the difference between a feasibility questionnaire and a site selection visit?
A feasibility questionnaire is a written survey a candidate site completes, usually the first step in the process. A site selection visit (also called a pre-study site visit, PSSV, or SSV) is a follow-up in-person or remote visit used to verify what the questionnaire reported and meet the site team directly, typically reserved for shortlisted sites rather than every candidate.
Who decides which sites are selected — the sponsor or the CRO?
It depends on the trial’s operating model. Sponsors running a trial in-house typically make the decision directly; sponsors working with a CRO commonly delegate day-to-day feasibility assessment and site scoring to the CRO’s site-management function, but retain final sign-off on the selected site list.
Does a site with no prior trial experience get automatically excluded?
Not necessarily. First-time sites are evaluated on proxies such as patient population access, staff qualifications, and infrastructure rather than a performance track record, and many sponsors deliberately include a portion of new sites in a trial to expand their qualified-site network, provided those sites pass the same feasibility and PI-qualification review as experienced sites.
What happens to sites that complete a feasibility questionnaire but aren’t selected?
They are typically notified of the outcome and, where the relationship is a good one, may be retained in the sponsor’s or CRO’s site database for consideration on future, better-matched protocols rather than being screened out permanently.
