Mass loss of precooked tuna muscle during retorting and storage in cans impacts cannery yield and throughput. Changes in moisture content and mass of frozen, thawed, precooked tuna muscle chunks, canned in water, were determined after retorting and through five weeks of subsequent storage. Canned tuna pieces were retorted to equivalent lethality (F o -value of four) for different time and temperature processes. Retorting at a lower temperature, longer time resulted in less mass loss than higher temperature, shorter time processes. Canned storage of up to five weeks had no effect on muscle mass or moisture content.