Adrenal cortical neoplasms in pediatric patients are rare. The clinical manifestations and biologic behavior of these tumors can be quite distinct from their histologically similar counterparts in the adult population. We report 5 cases of adrenocortical neoplasms in young children and review their clinical presentations, pathology, and follow-up data. Pathologic evaluations included histology and immunostains with p53 and Ki-67. The patients were 3 girls and 2 boys, 13-28 mo of age. The patients all presented with virilization and other hormone-related symptoms for an average duration of 6 mo. Serum testosterone levels were elevated in 3 cases. Imaging studies revealed neoplasms in the left adrenal gland in 3 cases and the right adrenal gland in 2 cases. No evidence of disease was identified at any other site of the body. The tumors were grossly confined to the adrenal glands and ranged in diameter from 3 to 6 cm (mean 4.3 cm). Microscopically, the tumors had histological and immunophenotypic features characteristic of adrenocortical tumors. Additional features noted included capsular and/or vascular invasion, severe nuclear atypia, high mitotic rate (>15 mitotic figures/20 high power fields), and atypical mitotic figures. Necrosis was present in one case. Immunohistochemical staining indices for p53 and Ki-67 were >20%. After follow-up periods ranging from 5 mo to 9.5 yr, all patients were alive and free of disease. Despite histological and immunophenotypical evidence of malignancy, these localized adrenocortical neoplasms had a benign clinical course with no evidence of metastasis or recurrence. Age is an apparent prognostic factor as these patients were <3 yr old. Because of the discrepancy between pathology and clinical outcome, adrenocortical tumors in this age group should be classified as neoplasms of unknown malignant potential.