We report a theoretical study of unimolecular dissociation of the ethyl formate radical cation (C2H5OCHO+center dot). The potential energy surface (PES) of its 14 dissociation reactions, including the formation of CH2CHC(OH)(2)(+), CH2CH2CO+center dot, CH3CHCO+center dot, CH2OCHO+, HOCHOH+, HOCO+, CH3CHOH+, HCO2+, CH2OH+, C2H6+center dot, C2H5+, HCO+, and C2H4+center dot, was determined using G4 calculation. A kinetic analysis using RRKM calculations based on the PES obtained adequately explained the results of previous experiments, suggesting that the dissociation occurred statistically from the electronic ground state.