Background: Genital melanotic macules are poorly recognized lesions, which appear as isolated discrete macules. Their occurrence, usually as new pigmented lesions in adult life, can cause concern because they can mimic early melanoma. Objective: Our purpose was to define the clinical, histologic, immunohistochemical, and electronmicroscopic features of genital melanotic macules. Methods: History and clinical features of 10 patients (5 female, 5 male) were assessed in detail. Histologic findings were reviewed in 5 cases, and immunohistochemistry, with the use of the HMB-45 antibody, in 4 cases and electron microscopy in 3 cases. Results: Clinically the lesions varied in color, tan to dark brown/black, and size (0.5-2 cm). Histologic findings showed increased basal pigmentation without atypical features. HMB45 antibody staining was negative. Electron microscopy showed normal morphology and number of melanocytes but increased melanosomes and dermal melanophages. Conclusion: Genital melanotic macules are benign, asymptomatic, discrete areas of hyperpigmentation that occur equally in men and women. Histologic, immunohistochemical, and electronmicroscopic study confirms their benign nature. (J Am Acad Dermatol 2000;42:640-4.)