Black or brown pigmentation of the nail plate commonly results from melanin produced by melanocytes in the matrix secondary to inflammatory dermatoses or systemic medications. It can also be caused by a benign pigmented nevus in the matrix or malignant melanoma. We report two cases showing black discoloration of the finger nail which were histologically found to be acral lentiginous melanoma in situ. It follows that melanoma, when the cells are separated from the dermis by a basement membrane zone, will have a good prognosis. Total resection for the lesion, including the nail matrix and nail bed with a free margin of 0.5 to 1.0cm, may be adequate.