In a prospective study of the value of 67Ga scintigraphy in cases of multisystem malignant melanoma, 69 scans were obtained for 36 patients. No abnormality was found in 18 scans. In only 3 was there other evidence of disease. Of 54 sites of disease demonstrated by scintigraphy, 40 were correlated with other investigations: biopsy (5), surgery (7), autopsy (7), radiographic (13) or clinical (8). Metastatic melanoma was found in 37 (69%) of the sites. No such disease was found in 3 (5.7%). The life expectancy of patients with an abnormal scan was shorter than that of patients with a normal scan. Ga studies reliably indicated the extent of multisystem melanoma, and are of value in clinical management.