The sleep of eight volunteers (mean age 55) was recorded electrophysiologically while viloxazine 200 mg was taken daily for 3 weeks, preceded and followed by a week of matching blanks. The volunteers also made ratings of their feelings on visual analogue scales. Another 15 volunteers (mean age 34) took viloxazine 300 mg daily for 3 weeks, preceded and followed by 3 weeks of matching blanks, and they also made daily ratings of feelings. The drug diminished sleep duration and caused more frequent and longer transitions into wakefulness and drowsiness. Slow-wave sleep decreased and stage 2 increased. REM sleep was markedly reduced, especially initially, and there was a withdrawal rebound. Viloxazine impaired subjective concentration mood, and quality of sleep. Three volunteers, however, had striking mood elevation. The drug caused a small loss of weight, which correlated with gastrointestinal symptoms. Three older subjects experienced withdrawal vomiting and prostration. Viloxazine shares properties with imipramine and with amphetamines.