Choline acetyltransferase immunohistochemistry has identified a large group of cholinergic neurons in the pontine tegmentum. By combined immunohistochemical and enzyme histochemical studies this particular cholinergic cell group was found to contain an enzyme, NADPH-diaphorase, that can be visualized histochemically. Thus NADPH-diaphorase histochemistry provides a simple, reliable method to selectively stain the cholinergic neurons of the brainstem reticular formation. The resolution obtained by this novel histochemical technique is similar to that found with the Golgi stain, and it should therefore be of great value in morphological studies of this cholinergic cell group.