The separability of meat products from fish products is investigated to gain a better understanding of Japanese consumer choices in protein demand. Rather than view fish as a single homogeneous commodity, fish and seafood are categorized into several groups of products. Separability is investigated using a demand system approach in which a generalized system of demand equations is specified and used, first to identify if any of the alternative demand structures nested within the general system are appropriate for these data, and then, conditional on those results, to test separability of meats from fish products following Moschini, Moro, and Green. Results indicate that meats and fish were separable prior to 1990; however, when examined over the entire 1981-95 study period, they are not.