Three experiments were performed to determine the behavioral effects of acutely administered chlordimeform (1-56 mg/kg, i.p.) to male mice. In Experiment I, dosages of 30 and 56 mg/kg decreased the amount of time spent investigating a female conspecific. In Experiment II, large dosages of chlordimeform (30 and 56 mg/kg) decreased vertically directed activity (rearing) to a proportionately greater extent than horizontally directed activity (ambulation). In Experiment III, chlordimeform produced conditioned flavor aversions that were intermediate at 10 mg/kg and maximal at 30 mg/kg. In an additional experiment (Experiment IV), the LD50 for chlordimeform was determined to be 95.6 mg/kg. Behavioral effects were thus obtained at dosages that were approximately 10 to 30% of the LD50.