Seasonality of reproduction ofRoweia stephensoni, Pseudocnella sykionandNeostichopus grammatuswas compared using gonad indexes, gonadal tubule diameters, egg diameters and the abundance of spermatozoa in tubules from January 1992 until August 1993. All three species were dioecious and the populations studied did not deviate from a 1:1 sex ratio. Body sizes at first sexual maturity were 2.5–2.9 cm3forR. stephensoniandP. sykionand 3.0–3.9cm3forN. grammatus.The gonads ofR. stephensoniandP. sykionconsisted of a group of unbranched tubules of equal diameter, with males having more tubules of a smaller diameter than females. By contrast, the gonad ofN. grammatusconsisted of two tufts of multiple branched tubules. All three species had annual reproductive cycles, and inR. stephensoniandP. sykiongametogenesis occurred from March 1992 until August/September 1992, and gonad maturity was maintained until spawning in January 1993. By contrast, inN. grammatusgametogenesis occurred from July 1992 until September 1992, and gonad maturity was maintained until spawning in December 1992/January 1993. InR. stephensoniandP. sykiongonads never completely regressed whereas inN. grammatusgonads regressed after spawning.