OBJECTIVE—To investigate how patients included in trials on treatment in the early phase of acute myocardial infarction experience the consent procedure. DESIGN—A combined qualitative and quantitative interview concerning the patients' knowledge of the trial, their feelings about being asked to participate, and their attitudes towards the consent procedure. SETTING—Tertiary referral centre. PATIENTS—31 patients who had given written informed consent for their participation in randomised intervention trials of acute myocardial infarction. RESULTS—The patients interviewed had only fragmentary knowledge about the trial they were involved in. Most considered that reading and signing a consent form was an unwanted or unnecessary procedure. Instead, they would have preferred to have been given concise verbal information about the study. Most were willing to allow a physician to decide for them in the event of their being too ill to be asked about their participation. CONCLUSIONS—Patients who are asked to participate in intervention trials in the early phase of acute myocardial infarction often appear to lack sufficient knowledge to reach an autonomous choice. There were problems and disadvantages associated with the process of obtaining written informed consent in this particular situation, especially regarding the need for the patient to sign a consent form during the acute phase of the disease.