Observational studies report low adherence to chronic polytherapy indicated by the international guidelines for the secondary prevention of acute myocardial infarction. However, current scientific evidence does not allow to quantify how much of the distance from the guidelines is attributable to the patient's behavior, to the providers of local care (general practitioners, district, Local Health Authority) or to the hospital of discharge. A cohort of about 17,600 patients with incident myocardial infarction, discharged from hospitals of Lazio region was selected, with the aim to measure the adherence in real clinical practice. Pharmaceutical prescriptions recorded in the two years following discharge were collected and analyzed. Results show low adherence to polytherapy and substantial intra-regional variability and identify in the hospital of discharge the care setting most responsible for the variability found in adherence levels, even after two years from acute episode.