Objective:To determine whether lymphocytic infiltration of the endometrium accompanies human immunodeficiency virus (HIV) infection.Methods:Endometrial samples from 12 HIV‐infected women and from rigorously matched controls were examined. The following markers were used: common leukocyte antigen (CD45), T lymphocytes (CD3), monocytes‐macrophages (CD68), and CD4 and CD8 lymphocytes. Cell counts were performed without knowledge of HIV status. Factors considered in relation to these markers were menstrual symptoms, pelvic pain, peripheral blood CD4+ count, and time since seroconversion.Results:Histology showed conventional features of chronic endometritis in only one case. In the remainder, the endometrium of HIV‐infected women, compared with controls, showed an increase in CD45 cells (P< .02) and an increase in CD3 staining cells (P< .05). This appeared to be restricted to those with menstrual symptoms, and this group also had lower peripheral blood CD4 counts. There was no difference in cells of the monocyte‐macrophage series (CD68). In contrast to control samples, CD4 lymphocytes were infrequent or absent in the endometrium of HIV‐infected women, regardless of peripheral blood CD4 count or presence of menstrual symptoms; however, this was not universal, as one sample showed an area of dense CD4 cell infiltration. The ratio of CD4 to CD8 was reduced in HIV‐seropositive samples compared with controls (P< .02).Conclusion:We hypothesize that chronic endometritis of a nonclassical form may be common in advancing HIV disease, possibly directed against HIV‐infected cells or self‐determined antigens. This could be associated with morbidity and may represent a reservoir of infection. Endometrial depletion of CD4 cells is a common, but not universal, feature and may be independent of immune compromise.(Obstet Gynecol 1994;83:586‐93)