The migration of hydrogen in the phenylethen-2-yl radical is investigated by determining optimal geometries and barrier and reaction energies using several quantum mechanical methods. Rate coefficients and equilibrium constants are obtained using the calculated data and RRKM theory. Theoretical methods compared include PM3, MP2, B3-LYP, CASPT2, and G2MP2. The applicability of these methods and comparisons with two others, G2M and CBS-RAD proposed to improve treatment of radicals, are discussed. The results obtained at the most reliable level of theory produce reaction rates sufficiently fast for these reactions to play a role in high-temperature aromatic chemistry.