T-lymphocyte subsets in duodenal biopsies of human immunodeficiency virus type 1 (HIV-1)-infected patients were studied by immunocytochemical staining to determine the alterations of CD4- and CD8-cell subsets in comparison with HIV-1 antibody-negative controls and to examine the association with stage, gastrointestinal symptoms, and peripheral lymphocyte subsets and the influence of high-dose intravenous immunoglobulins. A significant decrease in duodenal CD4 cells (p less than 0.001) and CD4/CD8 ratio (p less than 0.001) follows HIV-1 infection when compared to HIV-1-negative controls, more accentuated both in patients of stage WR6 and suffering from diarrhea than in those of stages WR1-5 or without diarrhea. In addition, a significant increase in CD8 cells (p less than 0.01) could be found in HIV-1-infected patients, again with lower levels in patients of stages WR6 than WR1-5. A strong correlation was found between the intestinal and peripheral CD4/CD8 ratio (R = 0.80), but the correlation was weak if HIV-1-negative persons were excluded from analysis (R = 0.29). Treatment with high-dose intravenous immunoglobulins improved diarrhea in four of five patients; two patients gained weight. Diffuse lymphocytic infiltration of the lamina propria, villous atrophy, CD4- and CD8-cell percentage, and CD4/CD8 ratio were not influenced.