The distances and orientations among reactant centers in the active site of coenzyme B-12-dependent ethanolamine deaminase from Salmonella typhimurium have been characterized in the Co-II-product radical pair state by using X-band electron paramagnetic resonance (EPR) and two-pulse electron spin-echo envelope modulation (ESEEM) spectroscopies in the disordered solid state. The unpaired electron spin in the product radical is localized on C2. Our approach is based on the orientation-selection created in the EPR spectrum of the biradical by the axial electron-electron dipolar interaction. Simulation of the EPR line shape yielded a best-fit Co-II-C2 distance of 9.3 Angstrom. ESEEM spectroscopy performed at four magnetic field values addressed the hyperfine coupling of the unpaired electron spin on C2 with H-2 in the C5' methyl group of 5'-deoxyadenosine and in the beta-H-2 position at C1 of the radical. Global ESEEM simulations (over the four magnetic fields) were weighted by the orientation dependence of the EPR line shape. A Nelder-Mead direct search fitting algorithm was used to optimize the simulations. The results lead to a partial model of the active site, in which C5' is located a perpendicular distance of 1.6 Angstrom from the Co-II-C2 axis, at distances of 6.3 and 3.5 Angstrom from Co-II and C2, respectively. The van der Waals contact of the C5'-methyl group and C2 indicates that C5' remains close to the radical species during the rearrangement step. The C2-H-s-C5' angle including the strongly coupled hydrogen, H-s, and the C5'-H-s orientation relative to the C1-C2 axis are consistent with a linear hydrogen atom transfer coordinate and an in-line acceptor p-orbital orientation. The trigonal plane of the C2 atom defines sub-spaces within the active site for C5' radical migration and hydrogen atom transfers (side of the plane facing Con) and amine migration (side of the plane facing away from Coll).