Records were reviewed of 79 infants and children with acute Staphylococcus aureus pneumonia admitted to our hospitals during a 13½-year period from 1965 to 1978. Primary staphylococcal pneumonia was diagnosed in 61 infants (median age, 6 months) and secondary pneumonia (disseminated disease) was present in 18 children (median age, 5.5 years). Fever and signs of pleural effusion and respiratory distress were common in primary disease while fever and a toxic appearance were frequent with disseminated illness. Lobar consolidation was the most common initial roentgenographic abnormality and effusions were detected in 80% of infants with primary pneumonia and 61% of those with secondary disease. In the first 12 to 36 hours after admission 22 (28%) infants showed rapid progression of the roentgenographic abnormalities associated with worsening of the clinical condition. S. aureus was grown in blood cultures from 29% of patients with primary disease and from 89% of those with disseminated disease. The case fatality rate was 25%; factors having a significant adverse influence on the rate were admission before 1972, treatment with ineffective antibiotics, bilateral and/or multilobe pulmonary involvement and a white blood cell count of ≤10,000 cells/cu mm.