Scanning electron and light microscopic studies reveal significant changes in the endometrial histophysiology of the soft‐shelled turtle Lissemys punctata punctata during its seasonal reproductive cycle. Scanning electron microscopy shows the entire oviductal mucosa to be only slightly folded throughout the non‐breeding period (regressive, quiescent, preparatory and recrudescent phases). With the onset of the breeding phase, the mucosa shows extensive foldings and convolutions. The adluminal mucosal lining of the non‐breeding oviduct is covered by a tall, dense ciliary bed, interrupted by a few fissures and pits. Microvilli‐bordered secretory cells only appear amongst the ciliated cells during the breeding phase. Light microscopic study reveals the mucosal epithelium to be low pseudostratified columnar throghout the non‐breeding period. The breeding epithelium, on the other hand, is tall columnar and does contain clearly distinguishable ciliated and secretory cell types. Submucosal glands only appear for a short period (ovulation to oviposition) in the infundibulum and isthmus regions of the oviduct, but these glands are observed throughout the reproductive cycle in the tube and uterus. The secretory activity of the submucosal glands, which occur only during the peak breeding stages, involves release of vesicular secretory materials through the gland openings. The stimulated endometrial histology and activity during the breeding phase coincide with increased levels of serum estrogen and progesterone, whereas the regressed and inactive state of the endometrium is paralleled by decreased levels of these ovarian steroids. © 1995 Wiley‐Liss, Inc. Copyright © 1995 Wiley‐Liss, Inc.