OBJECTIVE To discover the present role of Primary Care (PC) in the early response to Acute Myocardial Infarction (AMI) in a health area, defining the diagnostic and therapeutic measures employed and whether these cause delay in thrombolytic treatment. METHODS Prospective, observational study of cohorts. METHODS Casualty departments at the primary and hospital levels. METHODS All AMI patients admitted to the only Intensive Therapy Unit (ITU) in a health area over a three-month period (No. = 28). RESULTS The patients were divided into two groups, defined by whether they had attended PC or hospital. The time elapsed before ITU admission, and the diagnostic methods and treatments in PC were investigated. Nine patients (32%) attended PC and 19 (67%), hospital. The average delay was 6.7 hours. The percentage of patients who were admitted to the ITU before four hours had elapsed was higher for those who had previously attended PC (p < 0.05; Chi squared, Yates correction). In PC neither ECG, nor anti-aggregants nor analgesics were used in any of the cases. Nitrites were used on 4 patients (44%). CONCLUSIONS Patients with AMI preferred to go directly to hospital. Initial care in PC did not necessarily lead to any delay in the thrombolysis: indeed it led to a higher percentage of admissions during the first four hours. There was insufficient use of diagnostic procedures and drugs in the initial stage of AMI in PC.