The effects of levo-alpha-acetylmethadol (LAAM) on locomotor activity and operant behavior were examined in rats. LAAM increased locomotor activity when given intraperitoneally (IP) at doses of 1 mg/kg and 3 mg/kg, but 10 mg/kg produced a slight decrease in motor activity over the 10-hour period. The largest increases and decreases in locomotor activity occurred 6--8 hours after administration of the drug. Other rats were trained to lever press for food pellets under a fixed-interval 90-second, fixed-ratio 10-response multiple schedule. LAAM only decreased rates of responding under the multiple schedule. Marked decreases in rates of responding under both components of the schedule occurred with LAAM was administered IP either 3 or 6 hours before the session at doses of 3 mg/kg and 10 mg/kg. The rate- decreasing effects of LAAM became greater the longer the interval between administration of the drug and initiation of the session.