The kinetic isotope effects (KIEs) have been studied in the reactions of chlorine and bromine atoms with four ethene isotopologues (C2H4, (C2H4)-C-13, C2D4, and C2H3D) using FTIR spectroscopy and the relative rate technique. Halogen atoms were produced by the photolysis of Cl-2 and Br-2. For chlorine the KIEs, defined as k(C2)H(4)/k(x), were: 0.738 +/- 0.024 (C2D4), 0.853 +/- 0.037 (C2H3D), and 1.061 +/- 0.023 ((C2H4)-C-13) and for bromine: 0.817 +/- 0.016 (C2D4), 1.09 +/- 0.13 (C2H3D), and 1.1172 +/- 0.0053 ((C2H4)-C-13). Uncertainties are given as 2sigma. These results are interpreted in terms of the fate of the atom-molecule adduct. The implications of the results to atmospheric chemistry are described.