Between 1968 and 1985, we treated 20 children for fibromatosis (also called desmoid tumor and aggressive fibromatosis). The primary sites included head and neck (seven patients), extremity (seven patients), and trunk (six patients). Lesions ranged from 3 to 18 cm in diameter. The tumors were smaller than 5 cm in 13 patients, and in seven patients they were larger than 5 cm. A total resection was not feasible in any of the patients with lesions larger than 5 cm. Ten of the 11 patients treated with wide local resection, in whom the margins were clearly negative or close, remained free of disease for six to 16 years. Nine patients required additional treatment with radiotherapy (nine patients) and chemotherapy (five patients). Two died of local disease progression. In the remaining seven children, the disease was controlled. We describe our strategies for managing this disease in a pediatric population.