Experiment 1 investigated component duration in a four-component multiple schedule designed to separate the effects of the preceding schedule of reinforcement from those of the following schedule of reinforcement. The preceding schedule in the preceding component had no consistent effect regardless of component duration. The following schedule was a powerful determinant of behavior, however, with higher response rates resulting from a following period of extinction. Moreover, the effect of the following schedule was greater with short component durations, which strongly suggests that component-duration effects previously found with multiple schedules are due generally to variation in the degree of control by the following schedule. Experiments 2--4 investigated the basis of the effects of the following schedule. In some situations differential responding in the following component was the controlling variable, but in others it was differential reinforcement in the following component. The results are consistent with the view that response rate during a stimulus is inversely related to the "value" of the following component, where the calculation of value must include both primary and conditioned reinforcement.