Compositional mapping by electron probe microanalysis is one of the most highly developed techniques for the characterization of laterally inhomogeneous microstructures on a micrometer scale. X-ray dot mapping, or area scanning, has been a qualitative analysis tool since the earliest development of the scanning electron microprobe. Quantitative compositional mapping has been developed in the last five years by devising procedures to perform under computer control a complete electron probe analysis at each beam location in a scanned field. Energy dispersive spectrometry (EDS), wavelength dispersive spectrometry (WDS), or combined EDS/WDS can be used for data acquisition in the mapping mode, permitting simultaneous mapping of 10 or more constituents. All corrections applied in the conventional single point quantitative analysis procedure are included in the compositional mapping procedure: deadtime correction, spectral deconvolution, standardization (k-value measurement compared to a known standard), and matrix correction [ZAF, ϕ(pz), etc.]. Additional corrections for instrumental effects on WDS defocussing or EDS collimation are applied as necessary.