Experiments with normal animals (10 sheep and 15 cows) revealed that the intravenous injection of bovicystan led to a considerable and dependable rise of the blood sugar for 2 to 36 hours the peak being at the 6th hour. The treatment of 95 freshly calved cows on 8 farms with signs of subclinical ketosis (ketonemia 22.4 +/- 1.9 mg%, ketonuria up to dilution of 1:2-1:16 and hypoglycemia 26.7 +/- 2.6 mg%) resulted in a 92.6 per cent total curative effect, consisting in the full inhibition of ketonuria, drop of the ketone bodies in the blood up to 16.5 +/- 1.2 mg%, on an average, and rise of the blood sugar up to 47.7 +/- 1.2 mg%, on an average. In 27.4 per cent of the treated cows ketonuria disappeared after the first injection, in 50.5 per cent - after the second one, and in 14.7 per cent only did ketonuria faded after the third injection of the preparation within a period of 24 hours. At the 48th hour following the last introduction of bovicystan there was an increase in the blood serum level of carotene and lactose, and a decrease in the level of inorganic phosphorus. One to three weeks after treatment with bovicystan in some 27.6 to 33.0 per cent of the cows on 2 of the farms signs of subclinical ketosis reappeared.