The fingerlings of a fresh water teleost fish, Catla catla exposed to sublethal concentrations of chromium for 1, 8, 16, 32 days of time brought changes in the hematological parameters like RBC and WBC count were studied in the present investigation. The heavy metal, Chromium, an industrial effluent; an aquatic pollutant enters into the food chain of ecosystems responsible for changes in the hematological parameters of the animals such as the fresh water fishes.