AbstractConformational effects on the one‐bond Cα, H coupling constant have been studied in cyclic oligopeptides containing glycine, alanine, sarcosine and proline. The conformational contribution to1J(Cα, H) can be described as being composed of apositivehyperconjugative term from the neighbouring N‐pzorbital and anegativeone from the carbonyl π‐system. For glycyl units, a quantitative relation between1J(Cα,H) and the vicinal interorbital angles Φ′ and Ψ′ is derived with maximum values ΔJ(Ψ′) = + 14.0 Hz and ΔJ(Ψ′) = −4.9 Hz. Applications to conformational analysis of cyclo (L‐Pro‐Gly)3, cyclo (D‐Ala‐D‐Ala‐L‐Ala‐D‐Ala