The purpose of this qualitative descriptive study was to examine reasons for participation in clinical research among older adults with mobility limitation. A purposive sample of 20 men and 20 women aged 70 years or older was recruited. Data were collected by audiotaped telephone interviews using a semistructured interview guide and transcribed verbatim. Participants expect privacy, professionalism by research staff, and respectful treatment. Benefits to protocol adherence include personal education, comparison of their health status with that of others, opportunity to maintain vitality, and altruism. Barriers to protocol adherence are apprehension, in particular a negative impact on their health care, randomization to the control group, and experimental drugs; and inconvenience. Factors promoting study completion are obligation, reciprocity, receipt of test results, health promotion, and socialization. Implications include meeting expectations, providing health education and study results to participants, reducing barriers to participation, and presenting opportunities for interaction with others.