We examined the sequential modulation of congruency effects using a task in which the irrelevant information shares the same stimulus dimensions as the relevant information but is presented at an earlier time. In Experiment 1, sequential modulations were observed within a stimulus modality but not between stimulus modalities. In Experiment 2, sequential modulations were observed across two sets of visual stimuli, even though the two sets involved distinct stimulus dimensions. Experiment 3 used the same stimuli as Experiment 2, but required different responses for the two sets of stimuli. In this case, sequential modulations were specific to the stimulus set. In Experiment 4, two stimulus sets were presented along two stimulus modalities, and sequential modulations crossed both set and modality boundaries. These results suggest that control processes obey flexible boundaries defined by task constraints. (Contains 7 footnotes and 5 figures.)