Previous studies in dogs have shown that experimental infarction produces myocardial sympathetic denervation not only in the infarcted area, but also in a region apical to the infarction. In these dogs MIBG myocardial scintigraphy detected denervation but returned to normal in a few months at which time reinnervation was shown to have occurred. Myocardial sympathetic denervation was studied with MIBG scintigraphy in ten patients after their first acute transmural myocardial infarction; scans were repeated at 4 months, one year and 30 months to follow the time course of possible reinnervation. Except during the first 48 hours following the infarction, no therapy except for antiaggregants was administered to the patients; during this follow-up period no cardiac events were seen. One week after infarction, comparison of MIBG images with perfusion scans revealed that the denervated area was larger than the infarcted area; no difference in MIBG uptake by the infarcted myocardium was found during the 30 months follow-up.