Genitourinary neurofibromas are rare and clitoral involvement in neurofibromatosis (NF) has been reported infrequently. However, when it occurs, clitoromegaly is often the presenting sign. In many cases, it is congenital. In 236 families with type 1 neurofibromatosis (NF-1) evaluated through the USF Regional Genetics Program between January 1982 and September 1993, four patients had clitoral involvement. In three, involvement was limited to the clitoris. Biopsy/surgical excision in two of them showed a neurofibroma in one and non-specific hamartomatous soft tissue overgrowth in the other. In the fourth patient, the involvement was asymmetric and extended to the labia majora and mons pubis. Endocrine studies and chromosomes in all patients were normal; there was no exposure to androgens, progestins, or coumadin. There was no gestational history of maternal luteomas. Review of the literature documented 26 patients with NF and clitoral involvement. Clitoral involvement in NF-1 appears to be more common than previously reported and the differential diagnosis of ambiguous genitalia should include clitoromegaly due to NF. Pathogenesis of clitoral lesions appears similar to other lesions of NF. Biopsy of such lesions appears to be justified only when malignancy is suspected.