OBJECTIVE: This study evaluated a brief educational video designed to enhance the informed consent process for people with serious mental and medical illnesses who are considering participating in treatment research. METHOD: Individuals with schizophrenia who were being recruited for ongoing clinical trials, medical patients without self-reported psychiatric comorbidity, and university undergraduates were randomly assigned to view either a highly structured instructional videotape about the consent process in treatment research or a control videotape that presented only general information about bioethical issues in human research. Knowledge about informed consent was measured before and after viewing. RESULTS: Viewing the experimental videotape resulted in larger gains in knowledge about informed consent. Standardized effect sizes were large in all groups. CONCLUSIONS: The videotape was thus an effective teaching tool across diverse populations, ranging from individuals with severe chronic mental illness to university undergraduates.