The feasibility of measuring bone lead concentrations in vivo using multi-photon energy absorptiometry has been investigated. The hypothesis is that the accuracy and minimal detectable concentration (MDC) of the absorptiometric method is comparable to that of the x-ray fluorescence (XRF) technique, with a de-minimus effective dose less than 1 mrem. A further hypothesis is that the absorptiometric method will permit measurements in anatomical locations inaccessible to XRF, with significantly shorter acquisition times. Computer simulations indicated that an MDC of 9.2 μg lead per g bone in an adult tibia, and 20.5 fig lead per g bone in a 5 y/o child's tibia, was achievable at effective radiation doses < 1 mrem using a 155Eu gamma-ray source. The MDC was found to be a function of the photon energies employed, the acquisition time/activity, and bone size (ray-path length), but not of bone lead concentration. Experimental measurements using 1 mCi ¹⁵⁵Eu and a high purity Ge spectrometer indicated an MDC of approximately 38 μg Pb/g water for a two-component system. The MDC increased to 92 μg Pb/g using 6 mm of A1 to simulate = 1 g/cm² of bone in a three-component system and the same counting conditions. The results suggested that precision can be further improved with higher activity and or longer counting times, since the variance was dominated by Poisson statistics. The accuracy of the method was within 15% down to about 32 ppm in vitro, but clinical calibration might be the major limitation of this technique in practice, and has to be further investigated. Sources of bias were mainly attributable to uncertainties in attenuation coefficients. While several important questions have been answered regarding the feasibility of an absorptiometric approach for detection of bone lead, other relevant issues still need to be resolved. Modification of the detector and electronics is needed to achieve a short measurement protocol with count rates up to 1 MHz, a limitation of the current HPGe spectroscopy system. Full development of an approach to subject-bysubject calibration of attenuation coefficients is also required.