A growing literature suggests that the degree to which distracting information can be ignored depends on the perceptual load of the task, or the extent to which the task exhausts perceptual capacity. However, there is currently no a priori definition of what constitutes high or low perceptual load. We propose that interactions among cells in visual cortex that represent nearby stimuli determine the perceptual load of a task, and that manipulations designed to modulate these competitive spatial interactions should modulate distractor processing. We found that either spatially separating the task-relevant items in a display or placing the target and nontargets in different visual fields increased interference from a distractor that was to be ignored. These data are consistent with the idea that the ability to ignore such distracting information results in part from the need to actively resolve competitive interactions in visual cortex, and is not the consequence of an exhausted capacity per se.