(3)J(H-alpha,H-beta)-coulpling constants deliver precious information on the population of the three favored chi(1)-rotamers in unfolded states of proteins. Here, a novel pulse sequence, tailored toward the NMR analysis of non-native states of proteins, the HN(COCA)HAHB experiment, is developed to measure (3)J(H-alpha,H-beta). In four subsequent INEPT steps, magnetization is transferred from H-N to H-alpha. In a COSY-like magnetization transfer step, dephasino of magnetization on H-alpha is quantified to determine the (3)J(H-alpha, H-beta)-coupling constants. Analysis of the measured homonuclear coupling constants, together with measurement of hetronuclear (3)J(N,C-gamma) and (3)J(C',C-gamma)-coupling constants, allows stereospecific assignment of the two diastereotopic H-beta-protons even in unfolded states of proteins, and the derivation of populations according to a Pachler-type analysis.