The reproductive cycle and sex inversion of the protandrous, tropical seabass, Lates calcarifer, reared in seacages in French Polynesia, were studied. In Tahiti, this species exhibits a single annual reproductive period from October to February beginning with the warm and wet season. Sex inversion begins at the end of this reproductive period in post-spawning males. The main histological features of this process were: degeneration of testicular tissue, appearance of peripheral female germinal cells, and centripetal proliferation of ovarian tissue. Completion of sex inversion required profound morphological changes in the gonads because of the strong dimorphism that exists between testis and ovary. All transitional gonads appeared morphologically smaller than testes and typically had a red-pink colour. About 45% of the three-year-old male stock underwent sex inversion, and males averaged smaller in size than did females and transitional fish.