This study was designed to investigate two personality variables that may influence the effectiveness of covert sensitization in reducing smoking behavior. These are GSR reactivity to stressors and GSR adaptation to repeated stressors. It was predicted that both high reactivity and nonadaptivity to stressors would facilitate covert sensitization therapy. Fifty-nine subjects underwent treatment and were followed up at 3, 6 and 12 week intervals. Subjects were distributed among four groups: A. High reactors, nonadaptive (15); B. High reactors, adaptive (14); C. Low reactors, nonadaptive (9); D. Low reactors, adaptive (21). The results demonstrate that the measure of reactivity to stressors is significantly related to the success of the treatment, but the relevance of the measure of adaptivity factor was not demonstrated.