Abstract: In this paper, the clinical, histopathological and electron microscopic observations are made in 7 cases of subungual melanoma (SM).In 5 cases SM were found in the finger nails and 2 in the toe nails, and 5 in the thumb or great toe nails (2 on the right, 3 left). Longitudinal black lines developed in the nail plate before the appearance of SM in 4 cases. The mean age of the occurrance of the black lines was 47.6 years, and the mean time from the occurrence of black lines to the SM formation was 7.3 years. Thus, early excision of the black lines should be performed to prevent the devlopment of SM. Most of the tumor cells were, large epithelioid cells, and in 3/7 of cases polymorphous cells were also observed.