Depending on the kind of participants required, sponsors of clinical trials use various recruitment strategies, including patient databases, newspaper and radio advertisements, flyers, posters in places the patients might go (such as doctor's offices), and personal recruitment of patients by investigators. Volunteers with specific conditions or diseases have additional online resources to help them locate clinical trials. Patients may search in the clinical trial databases provided on Gene Therapy Net, but they can also search directly on ClinicalTrials.gov to locate trials using a registry run by the U.S. National Institutes of Health and National Library of Medicine.

Please note that many clinical trials will not accept participants who contact them directly to volunteer as it is believed this may bias the characteristics of the population being studied. Such trials typically recruit via networks of medical professionals who ask their individual patients to consider enrollment. A number of patients also travel to other countries for medical treatment. See for more information the section Medical Tourism.