Severe zinc deficiency was induced in male and female rats by feeding them a purified diet containing 0.5 mg zinc per kg of diet. Symptoms of zinc deficiency included severe growth retardation, loss of hair and scaly paws. Zinc-metallo enzymes were measured in kidney, stomach, and intestine of male rats and kidney and intestine of female rats. Alkaline phosphatase per mg DNA-phosphorus (DNAP) and per gram wet weight of tissue was lowered compared to ad libitum fed controls in all organs of both male and female animals. Carbonic anhydrase was lowered in all organs of male rats. It was only slightly lowered in kidney of female rats and was higher than in controls in stomach of female rats. DNA-phosphorus per gram wet weight was higher than in the controls in all organs of male animals and in the kidney of female animals. Stomach of female animals showed the same DNAP-concentration in experimental and control animals.