The potential of alcohol absorbed inside the mouth to affect the accuracy of a breath alcohol test has been known since the advent of breath alcohol testing. Although large concentrations of mouth alcohol are normally due to the oral consumption of an alcoholic beverage, ethanol can also be absorbed in the oral cavity from a number of other sources, such as alcohol-containing mouthwashes, breath sprays, and aerosol medications (1,2). Mouth alcohol has been shown to normally disappear within 15–20 min on a non-drinking subject, and it drops to in- significant levels in a shorter period on drinking subjects (3–5). For this reason, an observation period is usually mandated to allow for the dispersion of alcohol in the oral cavity prior to a breath alcohol test being performed. Although there has been speculation on the ability of significant alcohol concentrations to be retained for even longer timeframes in the oral cavity due to the presence of foreign objects such as oral piercings, chewing tobacco, and gum, these claims have been proven false (6–8).