The HID kinetic isotope effect (KIE) for the reaction of methyl radicals with glycine in aqueous solutions at pH 10.6 equals 16 +/- 3. This result proves that the methyl radical abstracts a hydrogen atom from the methylene group of glycine and not an electron from the unpaired couple on the nitrogen atom. The rate constant of the reaction of methyl radicals with glycine at pH 7.0 is orders of magnitude smaller than that at pH 10.6.