Physostigmine, an anticholinesterase that increases the action of brain acetylcholine, induces rapid eye movement (REM) sleep in normal humans. In this study we show that man dreams during physostigmine-induced REM sleep. Seventeen normal volunteers were pretreated with methscopolamine and received one intravenous infusion per night of either placebo or physostigmine either ten or 35 minutes after sleep onset. Subjects were awakened at specific times after infusion and interviewed regarding any sleep mentation prior to awakening. Results indicated that dreaming occurred during physostigmine-induced REM periods but that physostigmine did not alter mentation during non-REM sleep. These dreams were similar to spontaneous REM sleep dreams in content, vividness, unusualness, and emotionality.