Stimulus repetition associates with neural activity reductions during tasks that elicit behavioral priming. Here we present direct evidence for a quantitative relation between neural activity reductions and behavioral priming. Fifty-four subjects performed a word classification task while being scanned with functional MRI. Activity reductions were found in multiple high-level cortical regions including those within the prefrontal cortex. Importantly, activity within several of these regions, including the prefrontal cortex, correlated with behavior such that greater activity reductions associated with faster performance. Whole-brain correlational analyses confirmed the observation of anatomic overlap between regions showing activity reductions and those showing direct brain-behavioral correlations. The finding of a quantitative relation between neural and behavioral effects in frontal regions suggests that repetition reduces frontally mediated processing in a manner that ultimately facilitates behavior.