Effect of treatment with p-bromo-methamphetamine (V-111), the serotonin depleting drug, on two way avoidance conditioning (CAR) was studied in raphe lesioned male Wistar rats. Both sham lesioned and raphe lesioned animals treated with V-111 showed increased avoidance acquisition and increased number of inter-trial responses. Lesions of the raphe nuclei increased by itself the number of avoidance responses, the treatment with V-111 however produced further facilitation of avoidance acquisition. These results are discussed in terms of the role oserotonergic system in the processes of learning and retention of CAR, and direct action of V-111 on serotonergic system of the brain is suggested.