The distribution of catecholamine containing neurons and fibers was studied in the rabbit medulla-pontine-tegmentum by the chloralhydrate-glyoxylic acid-formaldehyde method. There are fundamental similarities between the rabbit and the other mammals on the catecholamine distribution. Most of the catecholamine fluorescent cell bodies in the rabbit are located within the nucleus locus coeruleus, subcoeruleus and substantia nigra in the pontine tegmentum. They are more extensive than those of the rat, monkey and more connective than those of the dog and cat. There are two main catecholamine fiber systems at the medulla level. One is ventrolateral catecholamine pathway originating from the area corresponding to Al in the rat and the other is the dorsomedial catecholamine pathway originating from the area corresponding to A2 in the rat. These two pathways associate with the upper medulla oblongatae level. One catecholamine containing cell group extends toward dorsolateral in the nucleus reticularis lateralis of the rabbit, but it has not been found in the rat.