In truly standardless electron microprobe analysis, generated X-ray intensities calculated from first principles are combined with a detector efficiency model. Though already used for energy dispersive (ED) analysis, the application of this concept to wavelength dispersive (WD) analysis is problematic, mainly because the reflectivity of spectrometer crystals is not well known. However, the need to carry out standard measurements with every batch of WD analyses can be avoided by using stored intensity data, and interpolation may be used when no standard is available. An empirical adjustment factor allowing for changes in spectrometer efficiency with time can be applied as necessitated by the variability of the spectrometer characteristics and the accuracy required. A similar approach to background corrections, based on measured continuum intensities, can be used. While the convenience of standardless WD analysis is attainable only at the expense of reduced accuracy, it can have a useful role where high accuracy is not needed or as a preliminary to applying a more rigorous routine using standards.