A double-labelling immunofluorescence study of rat spinal dorsal horn was carried out with antisera to Met-enkephalin and somatostatin. Varicosities in laminae I and II were frequently immunoreactive with both antisera, and in addition some neuronal cell bodies in lamina II possessed both types of immunoreactivity. These findings suggest that enkephalin and somatostatin coexist in some axons within the rat superficial dorsal horn and that at least some of these axons are derived from local neurones.