The cook-related yield losses for different sizes of white (Penaeus vannamei) and brown (Penaeus californiensis) shrimp were determined for peeled product previously treated with different concentrations of sodium tri-polyphosphate solutions (STP) (2% and 4%). The shrimp were cooked in boiling water for different lengths of time prior to cooling in air for 15 min. The effects of shrimp size, different internal product temperatures, related cooking times, and phosphate treatment were measured in terms of yield loss. Increasing the internal temperature resulted in higher yield losses. The increase in STP concentration reduced yield losses for the different sizes and STP was found to be more effective in smaller shrimp sizes. (C) 2003 Elsevier Ltd. All rights reserved.