When cock spermatozoa were incubated at 41 C with fluid removed from tissue cultured oviducal cells, their motility, assessed at room temperature, was maintained for 4 or 5 days. Fertilizing ability was retained for one week after culture for two days at 41 C. These results were comparable to the duration of motility and fertilizing ability of spermatozoa incubated in the presence of cultured oviducal cells. The results indicated that the fluid removed from the tissue cultured cells contains a secretory product(s) capable of prolonging in vitro the motility and fertilizing ability of spermatozoa.