OBJECTIVES: To explore factors associated with delay time prior to hospital admission and in hospital amongst acute myocardial infarction (AMI) patients with particular emphasis on the delay time to the administration of thrombolytic therapy. METHODS: During a 6-year period we prospectively computerized pre-hospital and in-hospital time intervals for AMI patients admitted to the coronary care unit (CCU) direct from the emergency department (ED) or via paramedics, at Sahlgrenska Hospital, Göteborg, Sweden. RESULTS: Pre-hospital delay: independent predictors of a prolonged delay were increased age (P = 0.0007), female sex (P = 0.02) and a history of hypertension (P = 0.03). For AMI patients who received thrombolytic treatment and the only independent predictor of a prolonged delay was increased age (P = 0.005). In-hospital delay: for all AMI patients independent predictors of a prolonged delay were prolonged pre-hospital delay (P < 0.0001), increased age (P = 0.03) and a history of angina (P = 0.002), hypertension (P = 0.01) and diabetes (P = 0.01). For thrombolytic treated AMI patients independent predictors of a prolonged delay were prolonged pre-hospital delay (P < 0.0001), female sex (P = 0.02) and a history of diabetes (P = 0.02). CONCLUSION: Risk factors for both pre-hospital and hospital delay time could in AMI be defined although slightly different. Two factors appeared for both, i.e. increasing age and a history of hypertension.