Ab initio self-consistent field (SCF) calculations in a Gaussian orbital basis set have been carried out on both the equilibrium (open) and bridging (ring) structures of various β-substituted ethyl radicals (C2H4X, X = Cl, SH, and PH2) in order to study substituent 1,2-migration. For X = Cl the C2v symmetrically bridged (SB) structure is found at all geometric points to be above the C2H4 + Cl dissociation energy limit in a multiconfiguration (MC) SCF framework, although single-configuration unrestricted SCF calculations show very shallow minima (for 2A1 and 2B1 states) at long C2H4-Cl distances. In the MC calculations on the steeply repulsive 2A1 state charge transfer (C2H4 → Cl) is found to be an important stabilizing feature, suggesting a method for stabilizing the ring structure. Bridging structures (both symmetric and slightly unsymmetric) involving relative twisting of the methylene groups are found to be more stable than the SB structures. For both X = SH and PH2 the unrestricted SCF results for the ring structures are similar to that for C2H4Cl.