[en] The sugar conformation of a DNA decamer was studied with proton-proton ³J coupling constants. Two samples, one comprising stereospecifically labeled 2'-R-²H for all residues and the other 2'-S-²H, were prepared by the method of Kawashima et al. [J. Org. Chem. (1995) 60, 6980-6986; Nucleosides Nucleotides (1995) 14, 333-336], the deuterium labeling being highly stereospecific ≥ 99% for all 2''-²H, ≥ 98% for 2'-²H of A, C, and T, and ≥ 93% for 2'-²H of G). The ³J values of all H1'-H2' and H1'-H2'' pairs, and several H2'-H3' and H2''-H3' pairs were determined by line fitting of 1D spectra with 0.1-0.2 Hz precision. The observed J coupling constants were explained by the rigid sugar conformation model, and the sugar conformations were found to be between C3'-exo and C2'-endo with Φ_m values of 26 deg. to 44 deg., except for the second and 3' terminal residues C2 and C10. For the C2 and C10 residues, the lower fraction of S-type conformation was estimated from J_H1'H2' and J_H1'H2'' values. For C10, the N-S two-site jump model or Gaussian distribution of the torsion angle model could explain the observed J values, and 68% S-type conformation or C1'-exo conformation with 27 deg. distribution was obtained, respectively. The differences between these two motional models are discussed based on a simple simulation of J-coupling constants