ABSTRACTIn vivoandin vitrostudies using the histochemical fluorescence technique of Falck and Hillarp were made on the submaxillary and sublingual glands of the rat after the administration of catecholamines or dopa, or the incubation of slices of the glands with the same drugs. Catecholamines and in all probability also L‐dopa were found to be bound extraneuronally in the salivary gland parenchyma under the conditions of the experiments. It is probable that the present experiments visualize the same type of extraneuronal binding as has been found with biochemical techniques. It appears that a certain activity of the parenchyma is necessary for the binding to occur. Apart from being a source of error in the evaluation of biochemical measurements, extraneuronal binding may be of importance related to transmitter mechanism