Although adrenal scintigraphy with 131I-6 beta-iodomethyl-19-norcholesterol (NCL-6-131I) was used for the first noninvasive imaging of the adrenal glands, it has the disadvantages. These are: (i) relatively high radiation dose to patients, (ii) the long time required for completion of the scan. To solve these problems, 123I-labeled 6 beta-iodomethyl-19-norcholesterol (NCL-6-123I) was synthesized and was used for adrenal scintigraphy in 6 cases. Successful images were obtained with 185 MBq (5 mCi)-260 MBq (7 mCi) of NCL-6-123I, and optimal time required for the satisfactory scan was 2-3 days after the administration. The estimate radiation dose was reduced by using 185 MBq (5 mCi) of NCL-6-123I instead of 18.5 MBq (0.5 mCi) of NCL-6-131I. From the result of this clinical study, NCL-6-123I was preferred for the adrenal scintigraphy.