The Food and Drug Administration approved the use of pentazocine (Talwin) in July 1967. The first report of an adverse reaction induced by this drug was received by the American Medical Association Registry on Adverse Reactions in August 1967. Since then, 20 reports have been received. Seven (35%) of these reports cited the hallucinatory effect associated with the use of pentazocine, while the others reported symptoms that included drowsiness, dizziness, inability to think, vertigo, vomiting, euphoria, incoordination exhaustion, extrapyramidal effects, confusion, rhinorrhea, hives, nausea, muscular tremor, and tightness of the chest. In the labeling of pentazocine the manufacturer has pointed out that the drug also has been associated with these adverse effects: nausea, vertigo, dizziness or lightheadedness, vomiting, euphoria, hallucinations, disorientation, weakness, muscle tremor, insomnia, and allergic reactions including edema of the face. This communication concerns the seven individuals who experienced the hallucinatory effect associated with the use of pentazocine.