Abstract The hypothesis that gamma-aminobutyric acid (GABA) is a peripheral neurotransmitter was tested by determining whether GABA is present in enteric neurons. GABA was detected in the quail gut using high pressure liquid chromatography. GABA-like immunoreactivity was found in both enteric neural plexuses. Only a few neuronal perikarya, but many fibers were stained in each. GABA-immunoreactive neurons survived for over a week in vitro; therefore, they must be intrinsic to the bowel. These and earlier observations indicate that GABA is a peripheral (enteric) as well as a central neurotransmitter.