An antiserum to GABA was used on semithin resin-embedded sections of rat dorsal horn. Immunoreactive neurons were evenly distributed throughout laminae I-III and constituted between 24 and 33% of the total neuronal population within three laminae. Fifty Golgi-stained cells in lamina II were tested with the antiserum. Most of the islet cells examined were immunoreactive, although some small islet cells were not. None of the 14 stalked cells tested was immunoreactive. These results provide further evidence that the stalked and islet cells of lamina II form two distinct functional classes and suggest that the islet cells function as inhibitory interneurons.