Nuclear magnetic resonance imaging (MRI) of selectively excited protons has been used for magnetic field mapping in a 1.5 T whole body imager. The imaging has been performed with a modified two pulse SENEX sequence, adapted to single- or multislice operation. The usual spin-echo image is superimposed by field markers which are created by a periodic non-excitation. Results of the method in the fields of image quality control, influence of the susceptibility of an object, and shim and gradient current field response are presented.