The peroxidase-antiperoxidase immunohistochemical technique was used together with an antiserum to gamma-aminobutyric acid (GABA) to identify GABA-containing structures in the rat basolateral amygdala (ABL). Morphological characteristics of GABA-positive neurons in ABL indicate that they correspond to class II, and perhaps class III, local circuit neurons observed in previous Golgi studies. GABA-positive punctate structures resembling axon terminals were observed both in the neuropil and forming peri-cellular baskets around large unlabeled perikarya in ABL. These results suggest that the strong intrinsic inhibition noted in electrophysiological studies of ABL is due primarily to synapses of GABAergic class II neurons with class I projection neurons.