Identification of [14C]pipecolic acid (PA) receptors was attempted in the solubilized membrane fraction from rat cerebral cortex. Specific binding proteins for both PA and muscimol, a potent gamma-aminobutyric acid (GABA) agonist, were detected in the same preparation. Separation of labeled PA and GABA binding proteins by glycerol gradient centrifugation has shown labeled protein bands of similar sedimentation rates, suggesting that PA and GABA may be binding to identical proteins. It seems likely that the PA binding receptor either may possess the same sedimentation characteristics as that of the GABA receptor, or both GABA and PA which is an endogenous and weak GABA agonist may bind to the same receptor complex, if not to the same binding site.