The physiologic roles of the tubal endothelium and tubal secretions are as yet poorly understood. In this study, we examined the tubal surfactant-like materials (SF-phospholipids) found in the tubal endothelium and lumen in order to elucidate their roles in the maintenance and development of the zygote. Evaluation of tubal infertility based on the presence or absence of SF-phospholipids in human tubal endothelium and tubal secretions was carried out in order to determine the degree to which tubal function was intact. By using fluorescing phosphin E, we found fluorescence in both the endothelium and the tubal secretions throughout the entire length of the tubes. In electron microscopic observations of the tubal endothelium, we were able to identify high electron density, lamellar inclusion bodies, either scattered or clustered in the areas close to the tubal lumen, in both ciliated and secretory endothelial cells. These lamellar granules in the tubal secretions appear to be secreted by a merocrine process and are observed in the secretions as a dispersion. Tubes from the proliferatory phase and the secretory phase were evaluated with the following results. The constituents of the tubal secretions were found to be phospholipids and proteins. The phospholipids were most abundant at or around the time of ovulation. This material caused capacitation of sperm by inducing an acrosomal reaction in the hamster sperm penetration test.