Recent advances in multidimensional NMR methodology to obtain 1H, 15N and 13C resonance assignments, interproton-distance and torsion-angle restraints, and restraints that characterize long-range order have, coupled with new methods of structure refinement, permitted solution structure of proteins in excess of 250 residues to be solved. These developments may permit the determination by NMR of the structures of macromolecules up to 50-60kDa, thereby bringing into reach numerous systems of considerable biological interest, including a large variety of protein-protein and protein-nucleic-acid complexes.