Crustacean females typically grow faster and achieve a larger size than males of the same age. This has implications for aquaculture of such species. Sexual dimorphism may warrant separating males and females during culture to ensure consistent harvest size shrimp from a pond, or in extreme cases mono-sex culture may be justified. We conducted an experiment to study the sex specific growth pattern of Peneaus monodon to determine extent of sexual dimorphism in growth and onset of sexual dimorphism. Shrimp were communally reared in two earthen ponds. One pond was for broodstock development at a low stocking density (7/m 2) and the other was stocked at a commercial stocking density (9/m 2). In the broodstock pond, females grew faster than the males after 70 days of culture and consistently maintained an average female-superior difference of 6-10 g. In the commercial pond onset of sexual dimorphism was at 90 days of culture, after which females grew faster than the males. In both pond types, the weight of shrimp at the onset of sexual dimorphism was similar, at 15-20 g. Therefore we conclude that weight is more important than age in determining onset of sexual dimorphism for growth in P. monodon. Females were approximately 8 g heavier than males in both ponds after 169 days of culture, so sexual dimorphism will be a major contributor to variation in harvest size if males and females are not reared separately.