Complete hypophysectomy in male catfish Clarias batrachus elicits a sudden hyperglycemia, after two days of the operation.Along with a parallel rise in the alkaline phosphatase activity of the whole blood and the liver, a simultaneous fall was observed in the blood calcium, serum protein and liver glycogen and cholesterol contents.The sham operated fish did not show such alterations of significance.All the parameters rise quickly following injections of pituitary extract obtained from the male of C.bactrachus.