When a portion of primary somatosensory cortex is deprived of its normal inputs by peripheral nerve transection, intact skin surfaces represented in surrounding cortex come to activate the deprived zone within 2 months. We found that this cortical reorganization was accompanied by a marked decrease in the antibody staining of gamma-aminobutyric acid (GABA) within the deprived sector of cortex in monkeys surviving nerve injury for 2-5 months. In contrast, there were no apparent changes in cytochrome oxidase reactivity in the deprived cortex of these same monkeys. Reduced levels of inhibition could allow previously unexpressed connections to become potent. Thus, the regulation of the expression of GABA appears to be one mechanism for maintaining and altering cortical representations.