When the NMR method for protein structure determination was introduced in the early 1980s the new approach met with enthusiasm amongst NMR spectroscopists, as well as scepticism and disbelief by structural biologists until the simultaneous but independent determinations of the three-dimensional structure of the protein tendamistat by X-ray crystallography [1] and NMR spectroscopy [2,3] yielded virtually identical results [4]. Since that time, NMR has become a firmly established method for determining the threedimensional structures of proteins. More than 7800 structures in the Protein Data Bank [5] of March 2009 have been determined by NMR ( Figure 5.1). This remarkable achievement would not have been possible without the development of sophisticated computational methods to compute three-dimensional protein structures from NMR-derived conformational restraints, and by increasingly automated approaches for analysing multidimensional NMR spectra.NMR structure calculations can be performed in several ways that differ essentially by the extent to which the analysis of the spectra is automated. In a basic structure calculation, all spectra are analysed by the spectroscopist who also interprets the data and provides the structure calculation program with geometric restraints in the form of allowed interatomic distance ranges, ranges of allowed torsion angle values, and Protein NMR Spectroscopy: Practical Techniques and Applications, First Edition. Edited