The clinical presentation of the disease and the results of treatment in 42 patients with malignant peripheral neuroectodermal tumors (MPNT) entered into the Cooperative Ewing's, soft tissue, and neuroblastoma trials of the German Society of Pediatric Oncology were retrospectively analyzed. Within the Ewing's sarcoma trial, patients with chest wall lesions were particularly analysed for MPNT features. The period of observation ranged from 15 to 86 months; the median relapse-free time was 24 months. There were 28 male and 14 female patients, the median age of patients was 15 years (range, 9 months-23 years). Thirty-two patients had localized disease (M0), and ten patients presented with primary metastases (M1). The predominant location of the tumors was the thoracopulmonary region, followed by the extremities, the abdominal/pelvic, and head and neck region. Thirty-one of 42 tumors involved the adjacent bone. The disease-free survival according to Kaplan-Meier life-table analysis was 56% +/- 11% for Stage M0 patients at 3 years. Nine of ten patients with M1 disease showed progression of their disease. Most patients had combined modality treatment with surgery, chemotherapy and radiation therapy. Best results were obtained with extensive surgery. Radiation doses ranged from 20 to 60 Gy and could not be correlated with the outcome of the disease. Most recurrences occurred at the site of the primary tumor. In patients with primary chemotherapy after biopsy-proven diagnosis, the responsiveness of this disease to chemotherapy could be demonstrated. Combination chemotherapy containing anthracyclines and high doses of alkylating agents appeared superior.