We simultaneously obtained blood samples in emergency patients for ethanol content from both antecubital fossae using an alcohol prep pad on one arm and a non-alcohol-containing germicidal solution on the other. Fifty patients with ethanol concentrations greater than zero were statistically analyzed. Twenty patients surveyed had no measurable alcohol level by either technique. There was no significant difference in the blood alcohol concentration obtained by either method of skin preparation in both groups (P less than .01). Blood alcohol concentration incidentally obtained in the emergency department by routine isopropyl alcohol skin preparation is an accurate laboratory parameter.