Seventeen of 646 (2.6%) children registered on the Intergroup Rhabdomyosarcoma Study (IRS)‐I and pilot study for IRS‐II as of December 1977, had apparent intrathoracic primary soft tissue sarcomas. The primary tumor appeared to arise in the mediastinum in ten patients, the pleura in four, and the lung in three. The age range was 1–20 years (mean, 9.9 years), and the male/female ratio was 1.8. Tumor histologic type was embryonal in seven, alveolar in five, undifferentiated in four, and extraosseous Ewing's (EOE) in one. Fourteen patients (82%) had unresectable disease at presentation, while three had grossly resected disease. These children were treated according to the IRS‐I15 or a subsequent pilot study protocol. Nine of 15 patients (60%) completing induction therapy achieved a complete remission (CR) and three a partial remission (PR) (CR + PR rate 80%). Two of three patients with grossly resected disease (Groups I or II) are long‐term survivors (4+ years), while only one of ten (10%) who had unresectable gross residual disease after surgery (Groups III or IV) is known to be surviving free of disease more than two years. We conclude that the “group” dependent survival experience of patients with intrathoracic primaries appears similar to that observed in the IRS‐I Study as a whole, but that this particular primary site is associated with advanced disease at presentation and its attendant high mortality with the treatment used. Additionally, intrathoracic primary tumors occurred in older children and were more likely to be of undifferentiated histologic types than tumors from most other primary sites.