Histochemical changes in gonadal nutrient reserves correlated with nutrition in the sea stars, Pisaster ochraceus and Patiria miniata. 1. Pisaster ochraceus has an annual reproductive cycle in which the gonads increase in size rapidly from October or November and reach a maximum in March to May, after which spawning occurs. In Patiria miniata the gonadal cycle is less pronounced and less regular. In the course of this study, animals spawned in July 1965, May 1966, and May 1967. 2. Histochemical techniques indicate that in both species glycogen or a glycogen-like carbohydrate occurs in the germinal epithelium and the follicle cells of the female, and in the spermatogonia and primary spermatocytes. A storage carbohydrate which is not removed by diastase or amylase is abundant in oocytes in the form of yolk granules 0.5 to 1.5 mu in diameter. 3. Neutral lipid droplets and phospholipid granules are abundant in all oocytes but the smallest. In the testes, lipid droplets are seen only after prolonged starvation. 4. In both species prolonged starvation results in failure of the gonads to achieve their normal size increase. Such gametes as are seen in starving speciments appear histochemically normal in some instances; in other cases they seem to be undergoing breakdown. 5. The histochemical results concerning nutrient reserves of the gonads are generally in agreement with the biochemical findings of earlier workers.