The value and feasibility of performing routine twohour blood glucose determinations on all admissions to a general hospital was studied in 2,472 patients. A high percentage (13%) of positive results was obtained with more than half of these showing carbohydrate intolerance after glucose tolerance test. The number of positive reactions increases markedly with age. New criteria are needed for the diagnosis of diabetes mellitus in the inactive, sick, or aged patient, but the carbohydrate intolerance demonstrable on two-hour postprandial blood glucose tests appears to be of value in discovering the asymptomatic potential diabetic. The glucose tolerance test should be performed if diabetes mellitus is clinically suspected, even though the two-hour postcibum test is normal. Clinical acumen was rewarded with evidence of diabetes mellitus in 25% of suspects with normal postprandial glucose levels.