The sites of synthesis of the chromogranins A and B, and their potential processed peptides, were examined by quantitating the levels of chromogranin A and B mRNA in various regions of the human brain by Northern blot analysis. Chromogranin A and B mRNA expression in the brain is region-specific and confined to grey matter. In situ hybridization histochemistry detected chromogranin A and B mRNA in pyramidal neurons of human cerebral cortex. Cell-specific expression in subpopulations of cerebrocortical neurons suggest that chromogranin A and B gene products may play a role in central neuronal function.