This article synthesizes research findings regarding the effects of occupational therapy on the restoration of role, task, and activity performance for persons who have had a stroke, with the purpose of guiding practice and research. It is the first of a two-part review of studies. Part II synthesizes research findings regarding the effects of occupational therapy on remediating impairments. Part I includes 15 studies involving 895 participants (mean age = 70.3 years). Of these studies, 11 (7 randomized controlled trials) found that role participation and instrumental and basic activities of daily living performance improved significantly more with training than with the control conditions. We conclude that occupational therapy effectively improves participation and activity after stroke and recommend that therapists use structured instruction in specific, client-identified activities, appropriate adaptations to enable performance, practice within a familiar context, and feedback to improve client performance. Empirical research to verify these findings and to characterize the key therapeutic mechanisms associated with desired outcomes is needed.