The cases of eighteen patients who were treated for pyomyositis between 1970 and 1988 were evaluated. The diagnosis was often delayed because other primary diagnoses were considered, including muscle strain, synovitis, thrombophlebitis, and neoplasm, and because the symptoms were vague and prolonged (maximum duration, one year). The muscles around the hip and thigh were most commonly involved (twelve patients), and Staphylococcus aureus most commonly grew on culture (twelve patients). Computed tomography aided in the accurate diagnosis of the infection and of the extent of involvement. Incision, drainage, and antibiotic therapy eradicated the infection in all patients, and they had no residual functional limitations and minimum residual symptoms.