The present study deals with the effect of kerosene on the morphological, behavioural and physiological changes (oxygen consumption and rate of oxygen consumption) in the freshwater fish, Channa marulius. The experimental animals were collected from Bharath Fish Farm, Thiruvallor district, Tamilnadu. The fish were oxygen packed in polythene bags and brought to laboratory to acclimatize them with laboratory conditions. Water soluble fraction of kerosene water was used for LC50 determination. Each tank was filled with 20 litres of water with required concentrations of water soluble fraction of kerosene (100 to 800 ppm). Ten healthy fish were left in each tank for experimental purposes, after range finding assay. Percentage mortality at the end of 96hr was recorded. For the toxicological studies, the animals were subjected to different sub lethal concentrations of toxicants, viz., the water soluble fraction of kerosene at 75, 150, 300 ppm and a control (0 ppm), at 24, 48 and 96 hrs after regular intervals. The morphological and behavioural changes were observed and recorded. The physiological changes like, total oxygen consumption and the rate of oxygen consumption per unit body weight was studied by modified Winkler’s method (Durairaj, 1987). The results indicate that the rate of oxygen consumption was found to decrease in both acute and chronic exposure when compared with control. The results were plotted and discussed in details.