The randomized controlled trial (RCT) has become the most widely accepted research design for testing the efficacy of health care interventions. The purposes of this paper are to (a) introduce the essential elements of RCTs, and (b) discuss some of the special problems faced by occupational therapists in conducting and interpreting RCTs. The CONSORT (Consolidated Standards of Reporting Trials) statement is recommended as an introduction to the components of RCT quality. Problems pertinent to the study of the efficacy of occupational therapy and related interventions include the importance of: theory, background, and rationale; treatment fidelity; theory-based outcomes; management of non-masked (non-blinded) interventionists and participants; and multiplicity of statistical analyses. This paper can help practitioners judge the quality of an RCT, and it can help the profession work toward the development of a cadre of qualified researchers who can adapt the well-established methods of RCTs to the study of occupation-based interventions.