Generalized linear mixed models were developed for allometric relationships in Atlantic sea scallops (Placopecten magellanicus). These models used environmental covariates such as depth, latitude, geographic area, fishing pressure, population density, and season. This study makes several technical improvements to existing allometric models. We found depth, latitude, and geographic area to be important covariates in models for scallops on Georges Bank, whereas depth and fishing pressure were important for mid-Atlantic scallops. Our allometric relationships have important implications for stock assessment and fisheries management.