Aggressive fibromatosis is a rare soft tissue tumour with a high tendency to local recurrence, even after apparently adequate resection. Wide local excision with a margin of at least 3 cm, depending on the anatomical location, should be performed to improve rates of recurrent disease. There is no consensus concerning the role of radiotherapy in the treatment of these lesions. The clinical findings of 39 cases diagnosed between 1972 and 1991 were reviewed retrospectively. Local control was effected in 19 of 32 patients treated with surgery alone after a median (range) follow-up of 72 (18-236) months. There were 40 cases of recurrent fibromatosis in 15 patients. Local control was obtained in 13 of 14 patients who received radiotherapy using a wide-field technique and doses of more than 50 Gy over a period of 5 weeks after marginal or incomplete resection of primary or recurrent lesions (P < 0.001). The results suggest that in a selected group of patients with aggressive fibromatosis radiotherapy may effectively achieve control of residual disease after surgery without marked disfigurement and loss of function.