Effects of intravenous infusions of LSD (3.75, 7.5, 15 microgram/kg over 5 min; crossover N = 4) and tryptamine (0.04, 0.08, 0.12 mg/kg/min for 150 min; crossover N = 6) were compared to saline in intact cats through observation of five sleep/waking patterns. Electrocorticogram (ECoG) was analyzed for frequency band indices and mean amplitude and frequency. LSD increases wakefulness and drowsiness and decreases spindle sleep and rapid eye movement (REM) sleep during the first 75 min (period 1). The increase in active wakefulness and decrease in REM sleep persist during period 2, with an increase in spindle sleep thereafter. LSD increases delta index and ECoG amplitude, with a decrease in ECoG frequency; these effects peaked in period 2. Tryptamine increases wakefulness and drowsiness during period 1, with decreases in spindle sleep and REM sleep. The increase in quiet wakefulness and decrease in REM sleep persist during period 2, but no significant tryptamine effect is seen in sleep/waking patterns after infusion ceases. ECoG frequency increases during tryptamine infusion (periods 1 and 2), while ECoG amplitude increases during periods 2 and 3. Thus LSD and tryptamine both increase wakefulness, decrease spindle sleep, and decrease REM sleep.