Sixteen children with rhabdomyosarcoma have been studied and treated in the past 3 1/2 years. The most common site of tumor origin was in the head and neck region, but some arose in the extremities, urogenital system, and trunk. The tumors grew rapidly, infiltrating locally and metastasizing to lung, bone, lymph nodes, and other organs. In 3 children tumor cells were found on routine bone marrow aspirations. Delay in correct medical diagnosis was common, and treatment was unsatisfactory in most instances. Radical surgical excision was possible in only 2 patients, in 1 of these only after reduction of tumor size by chemotherapy. Radiation therapy and an antitumor compound clinically known as actinomycin D produced temporary regressions in some patients; cyclophosphamide was effective in others.