Two-component schedules of differential-reinforcement-of-low-rate were presented, where the contingencies specified separately two minimum interresponse times, t1 and t2, required for reinforcement, depending on whether the interresponse time was initiated by, in one case, a reinforced response (t1) or, in the other, a nonreinforced response (t2). A distinctive pattern of responding developed on each of the two contingencies. Duration of an interresponse time approximated t1 when the t1 contingency was in effect, and t2 when the t2 contingency was in effect. This relationship persisted even when t2 was shorter than t1, and responding at a higher rate on the t1 contingency would have greatly increased the rate of reinforcement. Increasing the value of t2 resulted in both longer interresponse times on the t1 contingency, and a higher probability of a response-burst on those occasions when the contingency switched from t1 to t2. The results indicated that both reinforced and nonreinforced responses functioned as discriminative events in determining the duration of following interresponse times.