Numerous studies have shown that the follicle walls surrounding mature vertebrate oocytes are capable of producing primary prostaglandins. However, very few studies have looked at the prostaglandin synthetic potential of other ovarian tissue components. In brook trout (Salvelinus fontinalis) and goldfish (Carassius auratus), mature follicle walls can produce prostaglandins E and F (PGE and PGF, respectively); however, it is apparent that several other tissues within the fish ovary also produce specific primary PGs. Incubation of stroma or connective tissue from brook trout and goldfish ovaries with [14C]-arachidonic acid resulted in a very significant production of PGE2, whereas small immature oocytes of both species produced primarily PGF2 alpha. While the function of the primary prostaglandins produced by tissues external to the mature oocytes is unknown, it is important to recognize that multiple sites for prostaglandin synthesis are present within the fish ovary.