The patterns of pulmonary involvement in 13 children with progressive systemic sclerosis were investigated. Eight patients (61%) had respiratory symptoms or signs and 7 patients (55%) had abnormalities on chest roentgenogram. Twelve patients (92%) had abnormal pulmonary function tests: 7 had restrictive disease, 2 had obstructive disease, 2 had small airway disease, and 1 had an isolated reduction in the diffusing capacity of carbon monoxide. Nine patients had the test performed during the first year of illness, 3 during the second year, and 1 at 5 years. All patients had abnormal pulmonary function tests when first studied. Subsequent pulmonary function tests over a period of 3 to 10 years (mean 6.2 years) showed substantial changes in only 2 patients (1 patient had initial worsening of diffusing capacity of carbon monoxide followed by normalization and another patient showed improvement of obstructive disease). Two patients died during follow-up, 1 of pulmonary hypertension, the other of severe restrictive lung disease and myocardial fibrosis. The major findings of this study were (1) high frequency of pulmonary disease in children with progressive systemic sclerosis, (2) early involvement of the lungs, (3) relatively indolent progression of lung disease, and (4) the prognostic importance of the severity of pulmonary disease. Pulmonary manifestations of progressive systemic sclerosis in children appear to be similar to those of affected adults.