Eleven cases of a distinctive previously unrecognized mesenchymal tumor that arises in the vulvar region in the prepubertal years are described. The tumors presented in the vulva (8 cases arising from labia majora) of prepubertal girls (range, 4-12 years; median, 8 years). The preoperative diagnoses were labial mass or swelling, not otherwise specified in 3 cases, hemangioma in 2 cases, lipoma in 2 cases, and lymphangioma and Bartholin cyst/lymphedema in 1 case each. The tumors were unilateral, ill defined, located in the submucosa or subcutaneous tissue, and ranged in size from 2.0 to 8.0 cm in maximum dimension. Microscopically, they were poorly marginated, hypocellular neoplasms composed of bland spindle-shaped cells in a variably collagenous to edematous or myxoid stroma, diffusely infiltrating between preexisting normal vascular, adipose, and neural tissues. No cytologic atypia was identified. Mitotic activity was minimal with no abnormal mitotic figures. The tumor cells were immunoreactive for CD34 (8 of 9 cases) but not for smooth muscle actin, desmin, and S-100 protein. Treatment was by local excision. From the follow-up data available for 9 patients, 3 patients showed locally recurrent tumor after 4, 6, and 13 months, respectively, of which the second case showed a second recurrence 18 months after the first excision. The term "prepubertal vulval fibroma" is suggested because it reflects the distinct features of this seemingly unique, previously uncharacterized, site- and age-specific mesenchymal tumor.