Minor hemoglobin fractions, HbA1a + b and HbA1c, were chromatographed and measured in seven clinically normal dogs and in seven dogs with diabetes mellitus. Concentrations of glycosylated hemoglobin, HbA1c, were significantly higher (P < 0.001) in diabetic dogs. It was concluded that this determination may be useful for monitoring glucose status and the effectiveness of insulin therapy.