The treatment of acute myocardial infarction changed when several trials reported that thrombolytic agents given within a few hours of infarction improved outcome. We present data from the Nottingham Heart Attack Register comparing 1982-84, when thrombolysis was not available, and 1989-90, when it was hospital policy to give thrombolysis to all patients who arrived within 6 hours of the onset of symptoms, in the absence of a specific contraindication. The number of patients referred with symptoms suggestive of acute myocardial infarction increased by 75% from 1982 to 1990; a diagnosis of "possible infarction" was made in about half of all patients in 1982-84 and 23% in 1989-90. Our current thrombolytic policy has had little impact on patient and general practitioner (GP) behaviour. The GP was contacted by most patients. The median time between the onset of a patient's symptoms and admission to hospital when the GP was involved was 229 min in 1982-84 and 210 min in 1989-90; when he was not involved in arranging the admission median times to admission were 89 min and 75 min, respectively. By 6 hours from symptom onset, 60% of patients had been admitted; by 12 hours, about 70% were in hospital and by 24 hours, 80%. Of 7855 patients admitted with suspected acute myocardial infarction in 1989-90, 4465 were admitted within 6 hours of symptom onset. Of these, 736 (16%) patients received a thrombolytic drug. 389 (9%) patients had a specific, documented contraindication to thrombolysis. Although we estimate that the policy has saved about 8 lives per year, it is not surprising that there has been no improvement in overall case fatality after myocardial infarction.