The purpose of this study was to identify major proteins synthesized by the human oviduct and to determine if the ability of the human oviduct to synthesize these proteins was correlated with a specific stage(s) of the menstrual cycle. Oviducts, obtained from normal menstrual and immediately postpartum women, were minced and cultured in the presence of labeled precursors. The culture medium was analyzed for newly synthesized proteins by electrophoresis, followed by fluorography. One-dimensional gel electrophoretic analysis of culture medium of oviducts obtained at midcycle revealed a major diffuse band in the 120,000-130,000 mol wt (Mr) region which was greatly diminished in intensity or nondetectable in the media of oviducts obtained at all other stages of the cycle. Two-dimensional gel electrophoresis resolved the 120,000-130,000 Mr region into two major proteins, one basic and one acidic. Both proteins were intensely labeled with glucosamine, and the basic protein also incorporated leucine and methionine. Western blots of culture media incubated with antibodies against human placental proteins (PP) demonstrated that PP4 and PP7 were released throughout the cycle, while PP14 was present only at the late luteal stage of the cycle. This study demonstrates that human oviducts continue to synthesize and release macromolecules during organ culture. Additionally, the synthesis of some of these proteins appeared to be stage specific. The Mr 120,000-130,000 glycoproteins are of particular interest since they were observed in medium from midcycle oviducts, a period when the oviduct participates in gamete transport and embryo development.