Overdoses of acetaminophen are an increasingly common cause of acute liver failure. This study examines knowledge about acetaminophen therapeutic usage and toxicity among emergency department visitors. Adult visitors in an urban/suburban emergency department waiting room was surveyed with a questionnaire; 103/138 (75%) approached completed the questionnaire. 18% of the subjects believed the maximum daily acetaminophen dose is > or = 5 g. When asked to identify acetaminophen-containing products, only 13% chose Percocet and 6% Vicodin Motrin was the medication respondents most frequently believed to contain acetaminophen. 52% did not know acetaminophen toxicity causes liver damage. No statistically significant differences existed with regard to sex, race and age; more female subjects routinely inform doctors about their acetaminophen use compared to males (64% vs 30%). Some study subjects have very limited knowledge regarding therapeutic use of acetaminophen and its toxicity.