Acetaminophen is a popular nonprescription analgesic that is often taken in overdose by adolescents during suicidal gestures. The authors hypothesized that most adolescents are naive about the toxic and lethal potential of acetaminophen in overdose. A one-page, 12-item questionnaire was administered to 169 high school students to evaluate their perceptions and knowledge in this area. Whereas only 22% of the sample underestimated the dose of acetaminophen necessary to cause harm, 40.5% underestimated the potential lethality of acetaminophen in overdose. Moreover, 17% of the sample did not believe one could ingest enough acetaminophen to cause death. The lack of knowledge about acetaminophen's potential dangerousness, its widespread availability, and an absence of early symptoms of hepatotoxicity make this medication highly dangerous to those adolescents who take it in overdose during parasuicidal behavior.