The MMT4 study was designed to explore an intensive chemotherapy regimen (MMT4-89) and the role of high-dose melphalan (MMT4-91) in children with metastatic soft tissue sarcoma, including extraosseous peripheral neuroectodermal tumor (PNET). Thirty-one patients with PNET were treated between 1989 and 1995 (11 according to MMT4-89 and 20 according to MMT4-91). Chemotherapy consisted of four CEVAIE cycles, each including three 3-week courses: CEV (carboplatin 500 mg/m(2), epirubicin 150 mg/m(2), vincristine 1.5 mg/m(2)), IVA ifosfamide 9 g/m(2), actinomycin 1.5 mg/m(2), vincristine 1.5 mg/m(2)), IVE (ifosfamide 9 g/m(2), etoposide 600 mg/m(2), vincristine 1.5 mg/m(2)). In MMT4-91 the fourth CEVAIE was replaced with melphalan 200 mg/m(2) with stem cell rescue. The CEV combination was evaluated as a window study. Surgery followed the second cycle. Radiotherapy was administered to post-surgical residual disease. The response rate was 55% after CEV, rising to 80% after the first CEVAIE. Twenty-five patients achieved complete remission (CR). Overall, the 5-year EFS was 22.6%: 36.4% and 15% for patients treated according to MMT4-89 and MMT4-91, respectively (P = 0.3). Local control was achieved in 77% of irradiated patients vs 45% of non-irradiated. Age >10 years was associated with significantly poorer outcome (P = 0.04). In conclusion, despite the high CR rate, intensive chemotherapy with or without high-dose melphalan appeared to have little impact on the survival of patients with metastatic extraosseus PNET.