The H3'-C3'-C4'-H4' torsional angles of two microcrystalline 2'-deoxynucleosides, thymidine and 2'-deoxycytidine.HCl, doubly 13C-labeled at the C3' and C4' positions of the sugar ring, have been measured by solid-state magic-angle-spinning NMR. A double-quantum heteronuclear local field experiment with frequency-switched Lee-Goldberg homonuclear decoupling was used. The H3'-C3'-C4'-H4' torsional angles were obtained by comparing the experimental curves with numerical simulations, including the two 13C nuclei, the directly bonded 1H nuclei, and five remote protons. The H3'-C3'-C4'-H4' angles were converted into sugar pucker angles and compared with crystallographic data. The delta torsional angles determined by solid-state NMR and X-ray crystallography agree within experimental error. Evidence is also obtained that the proton positions may be unreliable in the X-ray structures. This work confirms that double-quantum solid-state NMR is a feasible tool for studying sugar pucker conformations in macromolecular complexes which are unsuitable for solution NMR or crystallography.