The NISTmAb Interlaboratory NMR Study is a joint effort between 25 organizations to evaluate the performance of two-dimensional (2D) heteronuclear NMR as used to characterize the high order structure (HOS) of proteins, with the aim of harmonizing 2D-NMR methods to support industrial use of NMR as applied to mAb therapeutics. This study features nearly equal representation between laboratories from academia, government, and industry, including 4 laboratories from regulatory agencies.