C-H and N-H rotational-echo double-resonance (REDOR) NMR is developed for determining torsion angles in peptides. The distance between an X spin such as C-13 or N-15 and a proton is measured by evolving the proton magnetization under REDOR-recoupled X-H dipolar interaction. The proton of interest is selected through its directly bonded heteronuclear spin Y. The sidechain torsion angle chi(1) is extracted from a (13)Cbeta-detected Hbeta-N distance, while the backbone torsion angle phi is extracted from an N-15-detected H-N-C' distance. The approach is demonstrated on three model peptides with known crystal structures to illustrate its utility. (C) 2003 Elsevier B.V. All rights reserved.