The proposed project will investigate healthy volunteers' patterns of participation in Phase I clinical trials, attending to differences based on their racial and ethnic backgrounds. It focuses on the relationship over time between healthy volunteers' perceptions of the risks and benefits of trial participation and their decision-making and behaviors surrounding enrollment in those studies. The majority of healthy volunteers in clinical trials are serial participants, meaning that they enroll repeatedly in studies, so a longitudinal study design is needed to understand their patterns of participation in clinical trial. The project is designed with four primary aims: 1. Assess how participants' perceptions of the risks and benefits of Phase I participation change overtime; 2. Examine how participants make decisions regarding their participation in clinical trials - including continuing serial participation - and assess the consistency of their choices over time; 3. Document how participants' self-reported behaviors (a) affect the validity of clinical trials and (b) increase and/or mitigate harm that could come from serial participation, including behaviors that have health benefits; and 4. Compare participants' perceptions, decisions, and behaviors across racial and ethnic groups. This 5-year project is a prospective, longitudinal, qualitative study and includes 200 healthy volunteers (50 1st-times Phase I participants, 50 2nd-time participants, 50 3rd-5th-time participants, and 50 6th+-time participants) who will be followed for 3 years. They will participate in 5 semi-structured interviews (total of 880): at enrollment, 6 months, 1 year, 2 years, and 3 years. Participants will also maintain clinical trial diaries documenting their activities in Phase I studies between interviews. In each group, 10 participants will serve as controls and be interviewed only at enrollment and at three years. The control group will be used to evaluate whether the interviews and diaries have an unintended interventional effect on volunteers over the course of the study.