Glycohaemoglobin (GHb) was estimated in haemolysate from dairy cows by colorimetric (thiobarbituric acid reaction) and ion-exchange (batch chromatographic) methods. The percentage of the non-enzymatic glycosylation of red blood cell haemoglobin depends on the blood sugar level. In consequence of the low blood sugar level of bovines, bovine GHb exhibits a lower value than that of the other mammals. GHb level was 2.18% (+/- 0.73) and 2.39% (+/- 1.03) in ketonuric and non-ketonuric cows. respectively. The authors suggest that the lower GHb level of cows with subclinical ketosis (ketonuria) is an indicator of the animals' energy-deficient status in the previous weeks.