The use of fluorescent markers in double-labeling experiments reveals the presence of reticular and raphe neurons in the opossum's brainstem which innervate both the cervical and lumbar enlargements of the spinal cord by way of axonal collaterals. Such neurons were mixed with those innervating either the cervical or lumber enlargement alone and were found within the nuclei reticularis medullae oblongatae dorsalis and ventralis, the nucleus reticularis gigantocellularis, the nucleus reticularis gigantocellularis pars ventralis, the nucleus reticularis pontis and the nuclei obscurus and magnus raphae. In some nuclei over 50% of the neurons projecting to the cervical enlargement also innervate lumbar levels.