The reproductive cycle of a local population the aspidochirote Holothuria tubulosa in Kaštela Bay (Adriatic Sea) was analysed from July 1994 to August 1995 by histological examination and observations of macroscopic features of the gonads. Five gonadal stages were described: recovery stage, growing stage, mature stage, spawning stage, and post-spawning stage. The distinguishing features used to describe gonad stages in both sexes included the main features of reproductive cells and gonad wall. The reproductive cycle showed a clear annual pattern and was synchronous in both sexes. Spawning occurred during the warm season, from July to September, when the surface water temperature ranged from about 22°C to 26°C. From October to January individuals were in resting phase and had no gonads. In both sexes, variations in maturity indices were related to the seasonal changes in temperature.