To investigate the distribution of autonomic nerves in the human heart, six autopsied hearts without cardiovascular disease were studied by a histochemical method for acetylcholinesterase (AChE) and by an immunohistochemical method for tyrosine hydroxylase (TH). The density of nerve distribution was microscopically calculated by the point-counting method to evaluate regional distribution of the autonomic nerves. There were more AChE-positive nerves and TH-positive nerves in the atrium than in the ventricle, and more at the base than at the apex in the ventricle. There were more AChE-positive nerves in the subendocardial area than in the subepicardial area of the myocardium. In the atrium, AChE-positive nerves were more numerous than TH-positive nerves. On the other hand, there were more TH-positive nerves than AChE-positive nerves in the ventricle. Predominancy of the distribution density at the anterior to the posterior wall of the ventricle was observed for TH-positive nerves. The different distribution patterns of sympathetic and parasympathetic nerves could modify cardiac performance under both physiologic and pathologic conditions.