The authors investigate whether the islets of Langerhans can actually be regarded as "neuro-paraneuronal control centers of the exocrine pancreas" as was first suggested by Fujita and Kobayashi (1979). The question is discussed on the basis of the authors' electron microscopic findings regarding pancreatic innervation before and after truncular vagotomy. The results do not seem to support the above hypothesis which advocates that the intrainsular axons are principally engaged in the release of their transmitters into the capillaries in order to regulate, via the insuloacinar portal vessels, the exocrine function of the pancreas. On the contrary, the present data draw attention to the unambiguous assignation of intrainsular axons to endocrine cells, a point of question in line with several findings published in the literature including papers by the first supporters of this hypothesis. No change was observed in the innervation pattern of the effector cells after vagotomy.