To test whether mental activities collected from non-REM sleep are influenced by REM sleep, we suppressed REM sleep using clomipramine 50 mg or placebo in the evening, in a double blind cross-over design, in 11 healthy young men. Subjects were awakened every hour and asked about their mental activity. The marked REM-sleep suppression induced by clomipramine did not substantially affect any aspects of dream recall . Since long, complex and bizarre dreams persist even after suppressing REM sleep either partially or (...) totally, it suggests that the generation of mental activity during sleep is independent of sleep stage. (shrink)