OBJECTIVE To examine whether human chorionic gonadotropin (hCG) is involved in the regulation of interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, and leukemia inhibitory factor (LIF) secretion from cultured human endometrial cells. METHODS A mixed population of endometrial cells from six in vitro fertilization/embryo transfer patients was cultured and incubated with various doses of hCG (0, 1, 10, 50, 100, and 500 IU/ml) for 24 hr. IL-6, TNF-alpha, and LIF levels in the culture medium were measured with enzyme-linked immunosorbent assay. RESULTS IL-6 and TNF-alpha levels were stimulated by hCG in a dose-dependent manner. Stimulation of IL-6 and TNF-alpha levels by 500 IU/ml of hCG increased their production by 3.7- and 2.8-fold, respectively (P < 0.05). Stimulation of IL-6 by 100 IU/ml of hCG was also significant (P < 0.05). However, there was no significant effect of hCG on LIF secretion by endometrial cells (P = 0.31). CONCLUSIONS hCG is involved in the regulation of endometrial cytokine production from human endometrial cells in vitro. This finding supports the recently emerging notion that hCG could have important local roles within the uterus besides its well-known luteotrophic role on the corpus luteum for maintenance of pregnancy.