For the investigation on neurohumoral theory, I have studied histchemically the distribution of monoamineoxidase (MAO), noradrenaline fluorescing substance (NAdF1) and acetylcholinesterase (AchE) in various tissues. The hypothesis thereby was that neuron with AChE activity is cholinergic, and with MAO activity and NAd-F1 is adrenergic. In the course of study, however, some nerve cells with high activity of MAO were found to show marked reaction not only in cytoplasm, but also seemingly in nucleus. Sympathetic ganglia consist mainly cells of this “nuclear positive” type and this type was supposed to be the characteristic feature of adrenergic nerve cell.In muscle layer and gland cells of esophagus, MAO activity was moderately positive and AChE activity was almost negative, while cholinergic and adrenergic nerve fibers around those tissues were seen. In Meiss ner's plexus, MAO and NAd F1 activity was poor or almost negative, but Auerbach's plexus of esophagus, especially in the lower part, showed high activity of MAO (contained many “nuclear positive type” nerve cells) and NAd F1. Whereas marked activity of AChE was found generally in nerve cells and fibers of both plexuses.But MAO activity in Auerbach's plexus was extremely poor in operated materials of cardiospasm, and “nuclear positive type” cells were also hardly found.In muscle layer, nerve fibers and ganglions of trachea and bronchus, AChE activity was intensely positive, but poor or negative in bronchioli and alveoli, MAO activity in epithelium and muscle layer of trachea and bronchus is moderately strong, and many cholinergic and adrenergic nerve fibers around those tissues were seen. In bronchiolar and alveolar walls, MAO activity was strongly revealed.