PROBLEM: Cytokines form an important communication network between the mother and fetus. Defining the significance of these factors requires an understanding of their constitutive expression by maternal and fetal tissues. This study examines cytokine expression by human trophoblast. METHODS: A reverse transcription polymerase chain reaction (RT-PCR) technique was used to assess cytokine expression by choriocarcinoma cells (BeWo, JEG-3, and JAR) and term trophoblast. Placental digests were enriched for trophoblast by immunoaffinity (CD-9) columns. RESULTS: Interleukin (IL)-1, tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma were weakly expressed or absent in the choriocarcinoma cells. In contrast, these cytokines were expressed by term trophoblast. IL-6, IL-10, IFN-alpha, IFN-beta, and granulocyte macrophage-colony stimulating factor (GM-CSF) mRNA were detected in all trophoblast cells, except for a paucity of IL-10 expression by JEG-3 cells. CONCLUSIONS: Human choriocarcinoma cells and term trophoblast express cytokines that may regulate critical reproductive events. Expression of inflammatory cytokines such as IL-1, TNF-alpha, and IFN-gamma by term trophoblast could trigger labor or be a consequence of labor-associated events.