Of 357 patients with soft tissue sarcomas (STSs) who were registered between 1981 and 1986 in the CWS-81 study, 21 (5.8%) were younger than 1 year of age. Six cases were probably of congenital origin since they were diagnosed in the 1st month of life. There was no difference in clinical grouping (staging and primary site) between infants and older patients. The major histological subsets comprised 12 patients with embryonal rhabdomyosarcoma (57% vs. 44% in older patients) and five patients with fibrosarcoma (23% vs. 2% in older patients). Of 21 patients, 17 received chemotherapy. The response rate (tumor reduction more than 1/3) to exclusive cytostatics therapy within 7-9 weeks, of ten evaluable patients, was 100% (vs. 86% in older patients). Eight of the responders achieved complete remission after 16 weeks of therapy and are in continuous complete remission (CCR). Most patients received 20-50% of the recommended chemotherapy dose for older children, which was calculated using body surface area. No fatal or life-threatening complications were observed. The event-free survival rate for children younger than 1 year of age with rhabdomyosarcoma was 70% vs. 47% in older children (no significant difference). Now, 2-5 years after therapy all five fibrosarcoma patients are alive and free of disease. Our data indicate that children under 1 year of age with rhabdomyosarcoma have a slightly better prognosis than older children, when therapy modalities are adapted to age.