The distribution and morphology of gamma-aminobutyric acid (GABA)-containing neurons in the rat prefrontal, frontal and parietal cortex were examined using a specific polyclonal antiserum directed against GABA and the immunoperoxidase method. The reaction product was present in the cell bodies, as well as in terminals and some processes without using colchicine. The immunoreactive neurons were observed in all layers but their laminar distribution was different in each cortical area. The immunoreactive cells were more numerous: in layer II and layer V-VI of the frontal cortex, in the deep layers (IV, V, VI) of the parietal cortex and in layer II and layer VI of the prefrontal cortex. The neurons displaying a labelling both in perikarya and processes were classified as multipolar and bipolar neurons. We distinguished various subtypes in each category. Multipolar neurons: cells with a large round soma and thin dendrites radiating in all directions; small neurons with ovoid or angular soma; large neurons with multiangular soma; neurons with a piriform soma. Bipolar neurons: horizontal bipolar cells with ovoid soma and vertical bipolar neurons with fusiform soma.