Diagnosis: HIV-1 infection and longitudinal melanonychia. This diagnosis was suggested by the findings of the physical examination (figure 1) and laboratory data in conjunction with the sexual history of the patient's husband, who admitted on further questioning that he was sexually promiscuous with tourists and that he was participating in orgies involving intercourse with persons of both sexes. The patient had positive results of an HIV-1 ELISA and a Western blot assay. Her CD4 cell count was 116 cells/mm3, and her virus load was 185,000 copies/mL, as determined by RT-PCR (Amplicor; Roche). Subsequently, her husband also tested positive for HIV-1 infection. Longitudinal melanonychia may occasionally occur in the absence of other disease, particularly in dark-skinned subjects [1, 2], but several pathologic associations have also been described. Common causes include the following: melanoma [1, 2]; benign nevi [2]; trauma that results in subungual hematoma [2]; hydroxyurea [2, 3]; adriamycin, cyclophosphamide, and polychemotherapy [1]; antimalarials [2]; and tetracyclines [2]. Less frequent causes include onychomycosis [2], nonmelanocytic tumors [2], endocrinopathy [1], onychotillomania [4], sub ngual keratosis of the nail bed [5], Laugier-Hunziker syndrome (mela onychia with macular pigmentation of the lips and buccal mucosa) [2], pregnancy [6], and systemic lupus erythematosus [7]. In HIV-l-infected patients, nail pigmentation is typically seen after the introduction of zidovudine therapy. This is a common and well-described occurrence, especially in darkskinned individuals [8-13]. On the other hand, relatively few reports have been published that link nail color changes with HIV-1 infection in patients who are not receiving antiretroviral ther py [8, 1, 14-18]. Longitudinal melanonychia has been associated with diffuse mucocutaneous pigmentation [15]. Nail