Earlier liquid-phase EPR measurements at room temperature of the λ-CH proton couplings in the CH(X 3(X 4)- groups of ·C(X 1)(X 2)OC(O)CH(X 3X 4) radicals and in the CH 2(X 1)- groups of CH 2(X 1)OC(O)C(X 2)(X 3) radicals (where an X- is an H- or a simple substituent such as CH 3-) together with comprehensive INDO-MO-SCF investigations on these same species have allowed the conformational preferences of these radicals to be deduced. The experimentally observed long-range λ-CH proton couplings in these species were demonstrated to be sensitive probes of variations in preferred radical conformation induced by steric and electronic effects of the alkyl substituents. The present paper shows that measurements of the temperature dependence of the λ-CH proton EPR coupling constants in these two types of radicals can be used successfully to determine their preferred conformations at room temperature. The conformations so obtained confirm those previously assigned using INDO-MO-SCF calculations.