The intramolecular character of the oxidative cyanohydrin‐cyanoketone rearrangement has been proven by cross experiments using 14C‐labeled compounds. The shown stereochemical requirements of the reaction and its analogy to the hypoiodite oxidation [3] of monohydric alcohols lead to the formulation of a reaction mechanism involving an internal addition of a carbon radical centre to the triple bond of a cyano group. Copyright © 1968 Verlag GmbH & Co. KGaA, Weinheim