Objective: Assuring research participants' capacity to provide informed consent has become increasingly important in health and mental health research, and each study faces unique capacity-assessment challenges, possibly requiring its own screening tool. This article describes the development and preliminary testing of a capacity-to-consent tool constructed for a study of psychiatric diagnosing in a community clinic. Method: A 10-item screening device based on four legal standards for demonstrating capacity (understanding, appreciation, reasoning, and voluntarism) was created and tested with 68 adult patients entering the study. Results: Only five participants (7%) failed the screen, 61 (93%) passed. No participants who passed at entry were later found in psychiatric evaluations to lack capacity. Conclusion: The tool was effective in identifying persons who could not demonstrate consent capacity, thereby protecting prospective participants. (Contains 1 table.)