Morphological and histochemical changes in the follicular epithelium have been studied during folliculogenesis in the crow (Corvus splendens) ovary. The follicular epithelium is single-layered in primordial and early previtellogenic, pseudostratified in late-previtellogenic, multilayered in early vitellogenic and again becomes single-layered in late-vitellogenic oocytes. Two types of follicle cells have been distinguished on the basis of their structure and cytochemical properties. Some of the follicle cells separate from the follicular epithelium and invade the ooplasm where they seem to be reabsorbed by the latter. The amount of lipids and proteins increases in the follicular epithelium as the oocyte grows. Simultaneously the nature of lipids and proteins changes, as revealed by various histochemical reactions. The follicular epithelium, at all stages of follicular growth, shows moderate reactions for acid phosphatase and NAD-diaphorase. The significance of the structural and histochemical changes in the follicular epithelium during oogenesis have been discussed.