Studies on chronic toxicity (for 10th, 20th and 30th days) of sublethal concentration of zinc sulphate (a heavy metal at 8.82 mg/l) on certain haemato-biochemical profiles have been made in an Indian catfish, Heteropneustes fossilis (Bloch). Except blood glucose (which showed significant increase) both, plasma protein and blood urea registered statistically significant decrease as compared to control after chronic treatment of sublethal concentration of zinc sulphate in this fish. The details have been discussed in this paper.