Two infants developed a protracted pneumonitis with lower respiratory obstruction beginning at one month of age. Lung biopsy in one suggested a viral etiology whith prompted an extensive investigation of each infant for specific etiology. Virologic, serologic, immunologic, and electronmicroscopic studies indicated that cytomegalovirus was a major causative factor. The infections were apparently acquired at birth from infected maternal genital tracts and have persisted for prolonged periods of time. Evidence for gross immunologic defect as a precipitating cause was lacking. These infants serve to emphasize the possible pathologic potential of CMV when acquired in early life even in the absence of iatrogenic immunosuppression. © 1976 The C. V. Mosby Company.