Mean wet weights, prosome length-weight and prosome width-weight relationships are established for the later stages of the copepods C. carinatus, C. australis, A. tonsa, C. vanus, C. brachiatus and D. forcipatus from San Jorge Gulf. Individual biomass was estimated by the morphometric method. The potential model relating size and weight was selected for the best fit. Prosome width was a better weight predictor than prosome length in almost all developmental stages and both sexes of the species.