The isomerization and fragmentation reactions of glycine radical cation, [NH2CH2COOH]+̇, have been studied using the B3LYP density functional approach and the post-Hartree-Fock CCSD(T) method. The most stable isomer of glycine radical cation corresponds to [NH2CHC(OH)2]+̇. The isomerization reaction from ionized glycine, [NH2CH2COOH]+̇, to [NH2CHC(OH)2]+̇ presents a high energy barrier due to large geometrical distortions at the transition state and important electronic reorganization. In contrast, the fragmentation processes arising from the Cα-R cleavage NH2CH2COOH+̇ → NH2CH2+ + COOḢ and NH2CH2COOH+̇ → NH2CHCOOH+ + Ḣ appear to be more favorable. The effect of solvation on the isomerization and fragmentation reactions is discussed.