In the present research which was done during the period of July 1997 to June 1998, histological studies on maturation stages of 40 yellowfin tuna specimen (Thunnus albacares) were conducted. It was concluded that the ovaries of this fish had the following characteristics; Germination disk were not present. There were no difference among anterior, posterior and middle parts of maturity stage of ovaries. All observed ovaries were asynchronous. The ovaries had five maturity stages which were as follow: a) Immature b) maturing c) Ripening d) Ripe e) Spent Average dimension of oocyte in different stage are as follow: Immature (40µ); Ripening (<60µ) and Ripe (<120µ)
