The accuracy of absolute quantitation within thick, mineralized tissue specimens is influenced by count rate variations of characteristic X-rays during electron microprobe analysis. The variations occur for electron doses approximately greater than 10(-10) C/micrometer2 and are primarily dependent upon the light element fraction within the irradiated volume. Specimen preparation procedures affect both count rate dynamics and interpretatin of microanalytical results. X-ray intensity data acquird at initial electron exposure and utilized in standard matrix correction schemes will project valid elemental concentrations for known calcium compounds over wide ranges of specimen density. Measurement error could approach +/- 2-3% for the major elemental constituents in mineralized tissues, but only with appropriate control or interpretation of electron irradiation phenomena.