The objectives of this study were to determine the types of lipid synthesized and secreted by the bovine oviduct, and to determine whether lipid synthesis and secretion varied with stage of the ovarian cycle and oviductal region. Oviduct explant cultures were prepared from cows killed during either the follicular or luteal stage of the oestrous cycle. Both stage of ovarian cycle and oviductal region affected lipid synthesis by oviductal explants in vitro. More lipid was synthesized by explants from follicular than from luteal-stage cows. Ampullar explants synthesized the greatest quantity of total lipid, followed by the preampulla and isthmus. Separation of extracted lipids from cultured tissue by high performance thin-layer chromatography (HPTLC) resolved phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, cardiolipin, free cholesterol, free fatty acid, triglyceride and esterified cholesterol, all of which were synthesized during culture. The ampulla synthesized significantly more phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol than did the other regions. Culture supernatants from ampullary explants contained the most newly synthesized cholesterol when compared with other regions. The histochemical location of neutral lipid droplets in the epithelium of cultured explants paralleled the localization of radioactivity in autoradiographs of explant extracts. The results suggest that the oviduct synthesizes a variety of lipids, and that some of these are released into culture supernatants.