Investigations were carried out with a total of 276 high-producing and clinically healthy cows that had freshly calved on 11 farms, being divided into groups according to the extent to which ketonuria was present if al all. Whole blood and blood serum were sampled to determine the ketone bodies, blood sugar, erythrocyte and leukocyte counts, hemoglobin, inorganic phosphorus, Ca, Mg, total protein, carotene, and activity of the GOT and GPT enzymes as well as the activity of lactic acid dehydrogenase, alkaline phosphatase, aldolase, and leucine aminopeptidase. Studied were the body temperature, the pulse rate, and the respiration rate. It was found that on farms with ketosis in cows ketonuria was manifested most often after the ketone bodies in the blood rose to 10-12 mg%. At the same time the blood sugar level was lowered and as a rule it showed reverse correlation with the levels of ketonemia and ketonuria. In such cows there was a lowering trend with the Ca and carotene contents and the erythrocyte count, and the respiration rate was higher. There were no changes in the body temperature, pulse rate, leukocyte count, Ca, Mg, hemoglobin, protein, and the activity of aldolase. The activity of the other enzymes mentioned was higher, and it correlated positively with the rise of ketonemia and ketonuria. With diseased cows the activity of alkaline phosphatase only was shown to be lower, negatively correlating with ketonuria.