Because of a general impression that a substantial proportion of emergency medical problems requiring treatment or hospitalization was caused by unsuspected alcohol consumption, a study to question that impression was done on a population of urban emergency service patients. We evaluated blood samples taken from these patients for routine determinations for many reasons other than suspicion of alcohol use or abuse. Abnormalities in results of serum ethanol concentrations were found more frequently than abnormalities of concurrently determined serum electrolytes, urea nitrogen, or glucose. The frequency of abnormalities found was ethanol, 42%; carbon dioxide, 35%; glucose, 34%; chloride, 32%, sodium, 21%; potassium, 20%; and urea nitrogen, 13%. The high incidence of serum ethanol elevations in such hospital emergency service patients and the considerable potential usefulness of ethanol levels in diagnosis and management of a wide variety of medical problems suggest that determinations of stat, timed, serum ethanol concentrations are often indicated as an emergency study for urban populations.