The Electron "licroprobe X-!{ay Analyscr conceivcd b~' R C.\S'L\I:\G and A. Cl'!:'\ lEI( in 1949 has been developcd as an extremelv po\\'crful tool in spcctrochcmical analysis for a wide range of applications, ranging from qualitative elcmcntary distribution studies, to highly localiscd quantitatin analysis on a one micron scale. \\'ith the increasing number oi' versatile instruments, commcrcially available, the domain of applications - in metallurgy, solid state physics, mineralogy and geology, biology and medicine, arts and archeology - is rapidly expanding, particularly because reliable quantitative analyses can be achieved. It is well established that in multicomponent specimens, the relative x-ray intensity generated by the electron bombardment - i.e. the intensity ratio of the characteristic x-ray radiation emitted under identical experimental conditions by the specimen and a calibration standard - is not directly correlated to the elementary mass concentration. The use of a wide scale of carefully prepared homogeneous calibration standards is generally very tedious and restricted to binar)' systems. For more complex specimens, the conversion of recorded x-ra)' intensity ratios to elementary mass concentration requires, besides carefule selection of experimental conditions, an adequate correction calculation to take account oi' the various physical phenomenas occurring in the tarp;et - electron retardation, electron backseattering, x-ray excitation efficieney, fluorescence enhaneement by eharaeteristic and continuous radiation and x-ray mass absorption.