Biopsy and/or autopsy material from lymphoreticular and other organs was studied in 8 children with suspected acquired immune deficiency syndrome (AIDS). One or both parents of each of these children had one or more of the recognized risk factors for AIDS, such as intravenous drug abuse, prostitution, Haitian origin. The following histologic patterns were noted in the lymph nodes: (1) follicular hyperplasia with normocellular paracortex, (2) follicular hyperplasia with depletion of paracortex, and (3) atrophy of follicles with depletion of paracortex. Lymphoid interstitial pneumonitis (LIP), a previously unreported lesion in AIDS, was present in 4 cases. It is suggested that the pulmonary lymphoid lesion may be part of a more generalized lymphoid hyperplasia involving B cells. The gross and microscopic features of the thymus, available in 2 of the 8 cases, indicated that the immunologic defect in these children was not of congenital type. Pathologic findings can be helpful in the diagnosis of the syndrome when correlated with clinical and immunologic features of suspected cases and of the pulmonary lesion. The latter is of importance in deciding the type of therapy to be given for the pulmonary disease process.