The present study investigated the effects on pause length of varying the response requirements in a mixed fixed-ratio x chained fixed-ratio x fixed-ratio y schedule. In mixed fixed-ratio schedules, a run of responses which approximates the response requirement of the smaller fixed ratio occurs at the beginning of the larger fixed ratio. This run of responses is called a prime. In the mixed chain schedule, the number of responses in a prime equals the response requirement of FR x. In the present experiment, the variables controlling pause length after the prime and after reinforcement were investigated by varying the size of either FR x or FR y. It was found that the length of the postprime pause was a function of FR y, while the postrein-forcement pause was a function of FR x. These results are consistent with those obtained with other fixed-ratio schedules and indicate that the length of the postreinforcement pause is not determined by the average of the ratios in mixed schedules.