Several widely used methods for suppressing the "background" signal in H-1 magic angle spinning (MAS) NMR spectroscopy are based on the assumption of a significant difference between the B-1 radiofrequency field experienced by the sample (within the MAS rotor) and that felt by static components of the probehead (where the background signal is believed to originate). In this work, a two-dimensional correlation experiment employing inhomogeneous B-0 and B-1 fields is used to image the B-1 distribution in a MAS NMR probehead. The experiment, which can be performed on any spectrometer, allows the distribution of the B-1 field to be measured and also correlated with the spatial location of the NMR signal within the probehead. The method can also readily be combined with various "depth pulse" techniques for background suppression, allowing their performances to be more rigorously evaluated. (C) 2013 Elsevier Inc. All rights reserved.