[en] In conjunction with a study on the biological effects of accelerated heavy ions on rat spinal cord, we were able to assess the residual skin damage remaining 1 year postirradiation. In this study, rats were irradiated with 230-kVp fractionated doses of either X rays, carbon ions, or neon ions. Four radiation fractions were given at daily intervals. For the carbon and neon ion exposures, rats were irradiated in both the plateau and spread Bragg peak (4 cm) regions of ionization. Comparing doses that produced complete epilation with a slight suggestion of a residual radiation scar, it was found that the relative biological effectivesness (RBE) values 1 year postirradiation for the four fraction irradiations were: carbon ions (plateau ionization region), 1.06; carbon ions (spread Bragg peak ionization region), 1.88; neon ions (plateau region of ionization), 1.55; and neon ions (spread Bragg peak ionization region), 2.26. RBE values for production of paralysis after spinal cord irradiation (using the same X-ray total dose levels for comparison purposes) were in all cases higher than the RBE values obtained from assessment of residual skin injury