(Received 20th September 2006, revised 3rd March 2007) Summary: The effect of pH on the uptake of Cu and Cd along with their mixture on larvae of Penaeus penicillatus and Penaeus monodon was studied at the pH range of 5.30 to 9.00. The uptake of Cu and Cd increased with decrease of pH, as pH increased from 5.30 upto 8.34 the accumulated concentration of Cu and Cd decreased. The lethal pH found in this study was 2.5 and 9 at which all larvae died within one hour even in control sample. The lethal pH at which minimum survival rate as well as highest accumulation as observed was 5.30.There was a marked effect of pH on the uptake process of Cu and Cd, which was found to be directly proportional to the exposed concentration in media. The minimum acceptable pH was calculated at which survival rate was reduced up to 50 % over each successive developmental stage of larvae. pH was therefore found to be an effective factor for controlling survival of shrimp larvae during shrimp rearing at culture plants.