The motivation for clinical trials inventory-depression (MCTI-D) was developed and evaluated for assessing motivations to participate in clinical trials on depression. Sixty-four participants completed the MCTI-D: 40 individuals expressing interest in participating in a randomized clinical trial (RCT); and 24 clinic patients receiving traditional care for depression. Content validity was supported by feedback derived from a panel of experts in depression research and respondents completing the measure. The motivation most frequently endorsed for participating in an RCT was the desire to help others and/or to further science. The potential stigma associated with seeing a psychiatrist was reported to have the least influence. Patients expressed a greater likelihood to participate in RCTs that involved psychotherapy than in experimental medication or placebo-controlled trials. Data from the MCTI-D may provide useful information for depression researchers to consider as possible influences on patients' decisions about whether or not they will participate.