Properties of a conditioned inhibitor (CI) were studied using the conditioned emotional response (CER) method. The classical defensive response (suppression of the on-going barpressing for food) was first established using 3 min of the white noise conditioned stimulus (CS) and foot shock unconditioned stimulus (US). Then the conditioned inhibitor, a 4 min house light offset, was introduced. During the last 3 min the CI was presented together with CS and not paired with the shock. The rapidly of CER training and also the efficacy of the CI training were both positively correlated with the CS intensity. The final effect of the CI + CS complex enhanced barpressing, whereas the CS alone suppressed it as before. The extinction of the CER resulted in the recovery of the regular barpressing rate during the CS and the CI + CS complex. Presentations of free shocks resulted in a temporary reinstatement of the suppressing effect of the CS and the enhancing effect of the CI + CS. The efficacy of inhibitory training depended on the alimentary motivation level.