Cardiac sarcoidosis is potentially fatal and hence requires a precise diagnosis. We performed dual (67)Ga (Ga)-(99m)Tc-sestamibi (Tc) single-photon emission CT (SPECT) scans by superimposing a Ga-SPECT image on the myocardial outline traced with Tc. The usefulness of this imaging technique in the diagnosis of cardiac sarcoidosis was studied. The subjects in this study were 14 patients with sarcoidosis (mean [+/- SD] age, 52 +/- 16 years; 5 men and 9 women). An IV dose of Tc (74 MBq per 2 mL) was injected into patients 72 h after an IV dose of Ga (111 MBq per 3 mL) was injected. The dual SPECT scan was performed 30 min after the Tc dose was administered. The energy used for collection was 93 keV for Ga and 140 keV for Tc. The myocardial outline was successfully traced in all subjects, allowing us to check for myocardial Ga uptake and to identify its location. Abnormal Ga uptake in the myocardium was observed in 9 of the 14 subjects. In seven of these nine subjects, the location of the abnormal myocardial Ga uptake was identical to the location of reduced Tc uptake. Abnormal Ga uptake disappeared in all cases following steroid therapy. Of the five subjects who were free of abnormal Ga uptake, two showed reduced Tc uptake, and these two subjects had been receiving steroid therapy. These results suggest that dual SPECT scanning using Ga and Tc represents a very useful diagnostic imaging technique since it improves the diagnostic capability of Ga-SPECT to allow the highly specific diagnosis of cardiac sarcoidosis.