OBJECTIVE: To study prehospital behaviour of patients admitted with acute coronary syndrome or witnessed cardiac arrest. DESIGN: Structured interview of 250 consecutive patients with acute coronary syndrome and relatives of 48 patients with witnessed cardiac arrest. The following courses of action were studied: contact the emergency medical service (centre); contact the general practitioner from the emergency service or the general practitioner during working hours; self-transportation to the emergency department; or as the first action to call the emergency medical service. RESULTS: Forty-four per cent of the patients admitted with cardiac arrest expressed no prior symptoms. Two-thirds of patients with typical symptoms interpreted it as cardiac-still only half took action within 20 min. Fifty per cent of patients who called a physician were delayed by wrong advice or misinterpretation. One hundred and thirteen patients (45%) knew of thrombolytic therapy. Twenty-seven of 75 patients with knowledge of the benefit of prompt treatment with thrombolysis, acted in accordance with this awareness. CONCLUSION: Patients misinterpret symptoms of acute coronary syndrome and are misguided when calling for medical assistance. Perceiving jeopardy had positive influence on the behaviour. Awareness of therapeutic options influences the decision-making process.