OBJECTIVE: To assess the impact of providing an educational videotape, 'Treatment Choices for Ischaemic Heart Disease: a Shared Decision-Making Program Videotape,' to patients referred for coronary angiography compared with standard patient-physician decision making (usual care). STUDY DESIGN: Randomized controlled clinical trial. SETTING: University Hospital and Veterans Affairs Hospital. PATIENTS: A consecutive sample of 217 patients referred for coronary angiography were randomized to receive 'usual care' or to receive the videotape in addition to standard patient physician decision making (videotape): 109 completed the study (50% completion rate). MAIN OUTCOME MEASURES: Knowledge of coronary artery disease, satisfaction, self-reported physical and mental health functioning, and the proportion of patients who were referred for coronary revascularization. RESULTS: Compared with patients who received 'usual care,' those who received the videotape were more knowledgeable (mean score 83 vs. 58%; P < 0.0001) but less satisfied with their treatment (79 vs. 88%; P = 0.038). There were no significant differences between the videotape and 'usual care' groups with respect to satisfaction with the decision making process (mean score 73 vs. 77%; P = 0.37), satisfaction with the decision made (mean score 73 vs. 78%; P = 0.28), physical functioning (38 vs. 38%; P = 0.76), mental health functioning (49 vs. 49%; P = 0.94), or in referral for coronary revascularization (OR 0.60; 95% CI 0.22-1.65; P = 0.33). CONCLUSION: Although the educational videotape increased patients' knowledge level, it was associated with a decrease in their level of satisfaction with treatment. Before there is wide-spread dissemination of this technology, advocates should demonstrate its effectiveness in everyday practice.