The gamma amino butyric acid antiserum was quality control tested using standard immunohistochemical methods. The antiserum demonstrates strongly positive labeling of rat thalamus and cerebellum using indirect immunofluorescent and biotin/avidin-HRP techniques. Recommended primary dilutions are 1/15,000- 1/20,000 in PBS /0.3% Triton X-100 - biotin/avidin-HRP technique. The specificity of the antiserum for GABA was evaluated using a competitive inhibition ELISA. While conjugates of GABA completely eliminate labeling, a 1000 fold excess of the following conjugates could not inhibit the antiserums ability to bind GABA conjugate: glutamate, aspartate, beta alanine, tyrosine, taurine, glycine and alanine.