The cerebral cortex of normal adult rats was studied by in situ hybridisation histochemistry, using digoxigenin-labelled oligonucleotide probes to preprosomatostatin (SOM). Labelled neurons were present in all cortical layers except layer I. They varied in staining intensity from light to heavy. There was no correlation between the size of the soma and staining intensity. A variety of neuronal types were SOM-positive. Some were clearly non-pyramidal, with a rounded soma and horizontal or oblique stem dendrites, while others had a prominent ascending apical dendrite and were interpreted as pyramidal neurons.