The present report describes the histopathological features of lymphoreticular tissues in 29 pediatric autopsies of human immunodeficiency virus (HIV)-infected patients. Mean age for the whole group was 1.77 years; 68.9% and 62% of the cases were 2 years old or less and 1 year old or less at the time of death, respectively. Twenty-one cases were categorized as acquired immunodeficiency syndrome (AIDS) and the rest included seven HIV-positive newborns and infants and two infants belonging to a high-risk group. The thymus (24 cases) showed severe lymphoid depletion (atrophy) in 16 (66.6%) cases, microcystic transformation of Hassall's corpuscles (HCs) in 4, calcified HCs in 3, absence of HCs in 3, and plasmacytic infiltrates and Warthin-Finkeldey-type multinucleated giant cells (also found in lymph nodes and bowel lymphoid aggregates in the same case) in 1. Lymph nodes (25 cases) revealed extensive lymphocyte depletion (68%); selective follicular (2 cases) or paracortical (3 cases) atrophy; hemophagocytosis (44%); some type of hyperplasia (plasmacytosis, enlarged follicles) in 5 cases; some type of lymphadenitis (12 cases), 5 cases of which were due to opportunistic infections (cytomegalovirus, 2; histoplasmosis, cryptococcosis, Mycobacterium avium-intracellulare, 1 each). Main findings in the spleen (28 cases) were extensive lymphocyte depletion (10 cases), limited to the white pulp in 4 and including the red pulp in 7; some type of lymphoid hyperplasia (limited to white pulp in 6 cases and involving the red pulp in 5); hemophagocytosis (7 cases); and foci exhibiting a peculiar arrangement of spindle-shaped cells combined with capillaries, plasma cells, and occasionally siderophages in 11. These we have termed kaposiform areas due to the resemblance to the so-called inflammatory variant of Kaposi's sarcoma. This pattern was also recognized in lymph nodes of two cases. Although atrophy was the main theme, cases with hyperplasia were also noticed. The possible relationship, if it exists at all, between kaposiform areas and Kaposi's sarcoma remains to be established. No tumor was found in this series. No specific histopathologic pattern of lymphoid tissues atributable to HIV emerged form this study aside from kaposiform areas, a microscopic feature not previously reported in this circumstance in pediatrics.