Steroid cell tumor of the ovary in a child. An 8-year-old girl exhibited severe, progressive virilization of 2 years' duration associated with markedly elevated circulating testosterone concentrations. Based on her initial clinical presentation and results of a chemical evaluation, she was originally thought to have non-classic 21-hydroxylase deficiency, but her condition did not respond to corticosteroid therapy. Further evaluation confirmed the presence of an ovarian neoplasm. The excised ovary contained an attached gray-brown mass. Light microscopic and ultrastructural examination revealed the mass to be a steroid cell tumor. Because Reinke's crystals were not present, it was designated to be a steroid cell tumor not otherwise specified. This case represents one of 22 reported cases of steroid cell tumor occurring in children described in the literature, most of which have been associated with heterosexual precocity. To our knowledge, steroid cell tumors are benign when they occur in prepubertal children. Although they are rare, steroid cell tumors of the ovary should be considered in cases of childhood virilization. 