By means of the indirect immunoperoxidase method glucocorticoid receptor (GR) immunoreactive nerve cells of the lower brain stem and the spinal cord have been mapped out in the rat, using a monoclonal antibody against rat liver GR. The GR immunoreactivity was predominantly located within the nuclei of these nerve cell bodies but also in glial cells of the gray and white matters. Strongly GR immunoreactive nerve cells were mainly found in the area of the noradrenaline, adrenaline and 5-hydroxytryptamine (5-HT) cell groups of the lower brain stem, and of the substantia gelatinosa of the nuc. tractus spinalis nervi trigemeni and spinal cord. The results suggest that glucocorticoids control transmitter and metabolic functions in discrete areas of the brain stem and spinal cord.