The efferent projections of the paratrigeminal nucleus in the rat were investigated by means of retrograde transport techniques. Injections were made in most of the supraspinal structures known to receive afferents from the spinal cord or the trigeminal nucleus caudalis. Spinal injections were also performed. Dense paratrigeminal efferents were seen to be directed to the nucleus of the solitary tract and to the peribrachial area, the latter including the cuneiformis and parabrachial nuclei. Projections were mostly ipsilateral. These results are discussed in relation to a possible role of the paratrigeminal nucleus in thermoreception and/or vegetative regulation processing.