A method for the demonstration of adrenergic nerves and enteric neurons at the same time has been developed by combining the fluorescence histochemical technique for catecholamines and the histochemical technique for NADH:Nitro BT oxidoreductase. The method consists of a short incubation of the laminae from the wall of the intestine in an isotonic medium containing the substrate (NADH) and a tetrazolium salt (Nitro BT). After washing, the laminae are air dried, exposed to formaldehyde vapour and mounted. The adrenergic nerves in the myenteric plexus appear brightly fluorescent on excitation with u.v. light, whereas the neurons are heavily stained by deposits of formazan. Not all the neurons of the plexus are stained, but their morphology is well preserved. Differences in staining of the neurons reflect differences in penetration of the tetrazolium salt in the tissue and into the cells. The adrenergic axons do not establish exclusive connexions with individual neurons and some isolated neurons are not associated with any adrenergic fibres.