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Three groups of Cebus albifrons monkeys (n = 4 in each) received instrumental conditioning of the skin conductance response (SCR), with periods of Sidman avoidance, response-contingent punishment, and brief times out from these contingencies. One group had previously received this conditioning with visual discriminative stimuli and was now given the same contingencies without the stimuli. A second group served as yoked controls for the first group. The third group received the conditioning without discriminative stimuli from the outset. After 24 sessions (1 hour, 2 per week), the first and second groups were terminated but the third group received 24 additional sessions with the visual stimuli added. The instrumental response was the unelicited SCR. Heart rate was also recorded. It was found that removal of the discriminative stimuli, in the first group, resulted in a significant reduction of the previously established difference in rate of SCR responding during avoidance and punishment (Favoring avoidance). This reduction resulted from an increase in response rate during punishment. The first group, nevertheless, still showed significantly more differentiation between avoidance and punishment than their yoked controls.