Using N-isopropyl-(I-123)p-Iodo-amphetamine (I-123 IMP) and gallium-67 citrate, it was possible to detect human malignant melanomas. I-123 IMP imaging was helpful in detecting melanomas occurring in the legs and arms, and the 4 hour image was better than the 1 hour image. Moreover, while gallium scintigraphy more clearly detects human malignant melanoma, I-123 IMP allows for the detection of human malignant melanoma within 1 hour after administration.