ABSTRACT Morphometric characters, gonadosomatic and hepatosomatic indices, and egg diameter of female Metapenaeus joyneri from the Zhujiang estuary, China, at different stages of ovarian maturation were reported. The minimum size of ovarian maturity was 16.1 mm carapace length. Spermatophore deposition in females was related to the ovarian maturation stage and could be used to monitor reproductive periodicity in this species. The presence of spermatophores in the terminal ampoule of males could be used as an indicator of male maturation state. The minimum size of male maturity was 10.9 mm carapace length. While the life cycle of M. joyneri appears to be confined to the estuary, the data suggest a movement of shrimp to the outer reaches of the estuary for mating and spawning.