Abstract Absolute and incremental K values (glucose disappearance rates) have been calculated with the aid of a computer from arterial and venous blood sugar levels obtained simultaneously during the 25-g intravenous glucose tolerance test and correlated with the fasting blood the peak blood sugar following the 25-g intravenous glucose load, the peak rise of blood sugar above the fasting level, the blood sugar 15 min. after the start of the 3 min glucose infusion, the blood sugar 60 min after the start of the infusion, the mean glucose uptake by the peripheral tissues over the whole test, 0–61 min, the mean peripheral glucose uptake from 13–61 min and the skinfold thickness. None of the K values regularly gave rectilinear slopes of decline of the blood sugar but absolute venous K values for the last phase of the test gave the highest correlation coefficients. The incremental K values did not discriminate between normal and diabetic subjects; heavy urinary glucose losses in diabetics probably account for the high glucose disappearance in these circumstances. Absolute K values did discriminate but this is due in large part to the height of the fasting blood sugar in diabetics. None of the K values correlated closely with the total peripheral glucose uptake but the absolute K values did with the fasting and 60 min blood sugar.