The present experiment was designed to determine the effects of 100%, 50%, and 0% reinforcement of nonresponse acquisition on the regular acquisition, latent extinction, and regular extinction of an instrumental running response. Ss were 78 male rats randomly assigned to six treatment conditions which included the administering of pretraining and training placements under varied reinforcement, followed by latent extinction and regular extinction test periods. Although the administration of pretraining and training placements had no significant effect on running speeds during acquisition, the results did indicate that Ss which had encountered nonreinforced placements prior to latent extinction were significantly more resistant to the effects of the pre-extinction placements. The discrimination hypothesis and frustration theory were considered as interpretations of the latent extinction data.