Of 144 pigmented lesions excised from the soles of Japanese patients, 140 were melanocytic. Apart from congenital melanocytic nevi, only a few benign acquired melanocytic nevi on the sole were more than 7 mm in maximum diameter and none exceeded 9 mm. In contrast, all plantar malignant melanomas, including malignant melanoma in situ, were 9 mm or more in maximum diameter. In addition, the majority of plantar melanocytic lesions excised from patients who were older than 50 years of age were malignant melanoma. On the basis of these data, we propose clinical guidelines for the early detection of plantar malignant melanoma.