Antiluteolytic actions of bovine interferon-tau (bIFN-τ) require suppression of prostaglandin F_2α (PGF_2α) production. Our objective was to test whether bIFN-τ could block PGF_2α production and synthesis of phospholipase A₂ (PLA₂) and cyclooxygenase-2 (COX-2) enzymes induced by a protein kinase C (PKC) stimulator (phorbol 12,13 dibutyrate; PDBu). Bovine endometrial epithelial (BEND) cells were treated with PDBu in the presence or absence of bIFN-τ. Medium samples were analyzed for concentrations of PGF_2α, whole-cell extracts were analyzed for abundance of PLA₂ and COX-2 by immunoblotting, and RNA extracts were examined for steady-state levels of COX-2 mRNA by Northern blotting. The PDBu stimulated production of PGF_2α between 3 and 12 h, levels of COX-2 mRNA by 3 h and protein expression of COX-2 and PLA₂ by 6 and 12 h, respectively. Added concomitantly with PDBu, bIFN-τ suppressed PGF_2α production, steady-state levels of COX-2 mRNA, and expression of COX-2 and PLA₂ proteins. Added after a 3-h stimulation with PDBu alone, bIFN-τ suppressed PGF_2α production after 1 h. Bovine IFN-τ inhibited intracellular mechanisms responsible for PGF_2α production in BEND cells, and this could be through both cytosolic and nuclear actions.