The subcutaneous intercellular glucose concentration was measured with a microdialysis method in 14 healthy volunteers and compared with that in venous blood. Under steady-state fasting conditions the intercellular glucose concentration was similar to that in the blood. During an oral glucose tolerance test the absorption phase was slightly delayed (approximately 2 min) in the intercellular space compared with the blood. However, the kinetics for the decline in glucose was similar in the two compartments. The interstitial glucose concentration was similar to that in venous blood during both a eu- and a hyperglycemic clamp. However, a rapid change from euglycemia to hyperglycemia was associated with a significant delay (approximately 8 min) in the intercellular glucose. The data demonstrate that the subcutaneous tissue glucose concentration under non-steady-state conditions closely resembles that in venous blood.