A Tl 201 scan was performed on one young patient who met all of the criteria for the diagnosis sarcoidosis. A resting scan before treatment showed marked defects which were not resolved on the redistribution scan, thus leading to the diagnosis of cardiac sarcoidosis, which was also suspected from clinical signs. After dipyridamole infusion (0.142 mg/kg per minute over 4 min), his 201Tl scan was quite normal. Haemodynamic investigation showed a low coronary sinus blood flow with a low lactate extraction: these abnormalities were fully reversed by i.v. dipyridamole infusion. Afterwards, the patient was given oral dipyridamole (450 mg/day) over 4 weeks; at the end of this treatment, his resting 201Tl scan was quite normal. These results suggest that myocardial perfusion abnormalities in sarcoidosis may be reversible after pharmacological vasodilation. Thus, in order to assess cardiac sarcoidosis, a resting myocardial scan should be performed before a scan after dipyridamole infusion. These results may have clinical, pathophysiological and therapeutic implications with regard to cardiac sarcoidosis.