The distribution of γ-aminobutyrate (GABA) and its synthesizing enzyme glutamate decarboxylase (GAD) in the epiphyseal growth plate of the rat long bone was studied by immunohistochemistry. GABA, GAD65 and GAD67 immunoreactive chondrocytes were found in hypertrophic zones of the growth plate, but not in reserve and proliferative zones. In the hypertrophic zone, GABA immunoreactivity was more intense in the maturation zone than in the degenerative zone and the zone of provisional calcification. Patterns of immunoreactivity for GAD65 and GAD67 were almost comparable to those of GABA. In addition, GAD65 and GAD67 mRNAs were detected by reverse transcriptase-polymerase chain reaction (RT-PCR). These results suggest that GABA, which is synthesized de novo in chondrocytes of the growth plate may have certain functional roles in skeletal growth.