Naevus unilateralis comedonicus is one of the rarest of the nevi and is characterized by grouped comedones unassociated with acne vulgaris. The comedones are large and occur in bands or groups which present a peculiar sievelike appearance. They are unilateral and in some cases are complicated by suppuration and scarring. We have been able to find twenty-nine cases in the literature. REVIEW OF THE LITERATURE In 1895, S. Kofmann1reported the first case, which was that of a man. aged 19. A strip of comedones extended from the superior posterior iliac spine forward and downward in a band, from 3 to 4 cm. wide; another band ran down the thigh, and a similar lesion on the outer aspect of the thigh extended to the outer condyle. The lesions had a sievelike appearance. They had been present since childhood. Biopsy was not made, but the condition was undoubtedly a