Histochemical techniques for lipids were employed to study the steroid synthesizing cellular sites in the ovary of teleost fish (Cyprinus carpio L.). The cellular sites of steroid biosynthesis appear to be the ovulating corpora lutea, interstitial cells, and special thecal cells of developing follicle. They possess the cytc-logical and histochemical features of well-established steroid gland cells. The functional significance of histochemical changes in the granulosa cells of post-ovulatory follicles in the teleost ovary has been discussed in the light of recent researches on corresponding cells in the ovaries of other vertebrates. The corpora atretica are merely the large yolky eggs in the process of their degeneration and resorption.