The current scenario to assess risk, particularly the regulatory limits for the use of pesticides mixtures are based on selective toxicological tests of the individual pesticides in the mixture and not on the basis of the combined toxic effects of the pesticides in the mixtures. The aim of the most of the toxicity studies being conducted usually with individual pesticides or mixtures of pesticides on aquatic organisms are to understand mortality, behavioral changes and changes. The reports on genotoxicity induced by the pesticides or in combination on fish are very limited. The pesticides that are proved to be non genotoxic using existing battery of tests may or may not be non genotoxic for ecologically important organisms. The analysis of DNA changes in aquatic organisms will be a useful tool to evaluate contaminants existed in the aquatic environments with genotoxic compounds. This book mainly focused on the studies to evaluate the genotoxicity of certain pesticide mixtures (Deltamethrin 1% + Triazophos 35% EC (D+T) and Profenofos 40% EC + Cypermethrin 4% EC (P+C)) in the ecologically important organisms like earthworm and fish.