The water pollution is a major problem in modern life. Almost all the heavy metals are toxic at higher concentrations and some are lethal even at a very low concentration. Among the heavy metals, arsenic forms a significant contribution to pesticides and industrial enffluents released into different water bodies. Pesticides used in excessive amount have caused potential health hazards not only to human but also to all of aquatic lives. It produces a variety of toxic effects in aquatic life including fishes. The freshwater fish Cirrhinus mrigala treated with two sublethal concentration of arsenic, have revealed a significant increase in the amino acid level in liver and tissues throughout the period of 28th days exposure. The present investigation has been designed to study the effect of total free amino acids in the selected tissues of C. mrigala. The effect might be due to intensive proteolysis in the respective tissues.