The kinetic hydrogen isotope effects in electrochemical reductions of CCl3COOD, CDCl2COOD, CCl4, CDCl3, benzyl chloride, 1-chloronaphthalene and 4-chlorobenzonitrile in deuterated reaction media were determined. The aliphatic chloro compounds are reduced with rather small isotope effects kH/kD= 1.2…1.7, as expected if anionic intermediates are formed and protonated. Benzyl chloride is reduced with an apparent kH/kD= 2.1, which is probably too high due to radical reactions. Aromatic chloro compounds are reduced with significant participation of a second mechanismviaradical intermediates which abstract carbon-bound hydrogen atoms from the components of the reaction system. The resulting isotope effects are kH/kD= 1.2 for the part of the reduction which proceedsviaanions and kH/kD∼ 2.5 for the competing radical reaction.