Rats highly trained to avoid shock in a shuttle box showed immediate extinction of avoidance responses following injection of 20 mg/kg amobarbital. Reduction in spontaneous recovery of the CAR was also a function of 20 mg/kg amobarbital treatment. Failure to perform the CAR in extinction and spontaneous recovery under 20 mg/kg amobarbital occurred with a strong competing freezing behavior which made the avoidant response impossible. Such effects were not amenable to explanation by the depressant or fear-reducing effects of 20 mg/kg amobarbital. Rather, it seemed more likely that amobarbital disrupted the CS-CAR connection, and that blocking of the CAR resulted in a very strong competing CER.