This study tested the hypotheses that the amplitude of the unconditioned GSR is gradually attenuated by the CS during conditioning and that this reduction in UCR amplitude vanishes when the CS is omitted and the UCS presented alone. Three groups of 10 Ss received either 4, 8, or 16 reinforced presentations of a tone CS and electric shock UCS in a classical delayed paradigm. Following reinforcement the CS was omitted and 2 UCS alone trials were administered. After the tests on the shock alone, 4 extinction trials of the CS alone were given. It was found that the amplitude of the unconditioned GSR diminished during reinforcement and that the UCR recovered to approximately its original amplitude when the CS was omitted. The amount of increment produced by omitting the CS was a linear function of the logarithm of the number of reinforcements. These results were interpreted as supporting the notion that a conditioned inhibitory process develops during reinforcement, under the control of the CS, which attenuates the amplitude of the UCR in the presence of the CS. The relationship between these findings and similar findings in a study of the relationship between amount of disinhibition and number of reinforcements was thought to add further support to the interpretation offered.