The interaction of schistosome eggs with venular endothelium was studied using primary cultures of human umbilical vein endothelial cells. Freshly oviposited and embryonated eggs of Schistosoma mansoni, Schistosoma japonicum, and Schistosoma haematobium were used. The cultures were evaluated by light, scanning, and transmission electron microscopy. Endothelial cell monolayers were found to retain eggs by actively migrating over those that came to lie on top of them. The monolayers then reestablished confluency and their lumenal polarity. Eggs deposited directly by adult worms elicited a more rapid and complete response than embryonated eggs isolated from the liver tissues of infected rodents or latex beads. Cell migration was shown to be more complete in the presence of sera than in serum-free media. It is concluded from these observations that eggs can be passively transferred to the perivenular space by the nonspecific response of endothelial cells.