The present series of experiments investigated behavioral changes in HET mice following administration of kanamycin, one of the aminoglycoside antibiotics. After drug treatment, HET mice showed changes in complex behaviors, including male agonistic behavior, female postpartum aggression, and tactile discrimination performance. Specifically, the temporal distribution of agonistic behavior appears to be affected by kanamycin treatment in both males and females, and kanamycin administration seems to alter reversal performance on a tactile discrimination task. These findings suggest the need for more careful examination of behaviors which may prove to be sensitive indices of antibiotic toxicity.