Radiation therapy (RT) is a highly effective modality in the treatment of sarcomas of soft tissue when combined with conservative surgery. RT followed by surgery is judged to have important clinical advantages over the reverse sequence. Of special significance to the treatment of the pediatric patient is the observation that the treatment volume in preoperative RT is nearly always smaller than in postoperative RT. Precise definition of the target volume and utilization of minimum treatment volumes (i.e., reduction of the treatment volume toward the target volume to the greatest extent technically feasible) are particularly important to the improvement of functional results. Data are described for 21 patients who were 21 years old or younger and were treated by RT and surgery and RT alone and who have been followed for 3 or more years. Local control of the treated tumor was achieved in all 21. Absolute figures for disease-free survival were 5 of 5 and 10 of 16 patients in the 6- to 14- and 15- to 21-year age groups, respectively. Survival results according to stages for the latter group were as follows: stage I, 4 of 4; stage II, 4 of 7; and stage III, 2 of 5. All 9 patients with fibrosarcoma or neurofibrosarcoma survived free of disease. The need for an effective chemotherapy regimen for patients in stages IIB--III is emphasized.