The present paper analyses a case of ovary assimetry verifier! in a specimen of Micropogon fumieri (Desmarest, 1822) Jordan, 1884, captured at San Antonio Cape, Argentina, between the 4th and the 12th of January, 1958. The specimen had the ovaries ful] developed and the following biometric characteristics: total length, 49,6 cm; standard length, 42.5 cm; maximum height, 12.5 cm; total weight, 1,710 g. The following conclusions were drawn: 1 - There was an assimetry of shape, weight and internal structure in the two ovaries; 2 - The right ovary had more ovules per unity of weight than the left one, although there was not a significant difference between the diameter of the ovules; 3 - We can suppose that the right ovary, smaller than the left one, tried to reach an equilibrium with the left one through an increase in the capacity of producing sexual cells per weight unity and so through the reduction of the intersticial materials; 4 - The assimetry was determined during the ontogenetical process and not by any pathological cause; 5 - We suppose that the embryologieal process responsible for the analysed assimetry is similar to the one that occurs among the birds, and so, that among the fishes the right gonada has more lability on the sex determining process.