Amitraz (AMZ), a formamidine pesticide, displayed a unique spectrum of neurobehavioral effects which differed from that of the prototypic formamidine, chlordimeform (CDM). In male Long-Evans rats, general signs of intoxication included hypothermia, hyperreactivity, vasodilation, profound weight loss, aggression, and extreme reactions to handling. These effects required days to weeks for recovery, and were cumulative with short-term repeated administration. AMZ produced differential effects on multiple-schedule performance that were distinct from the effects of CDM. Moreover, the marked signs of intoxication, and effects on schedule-controlled behavior following high doses (>50 mg/kg), were persistent and cumulative on repeated administration.