A 3-meV proton beam from the MP Van de Graaff accelerator at the Nuclear Structure Research Laboratory of the University of Rochester has been used to induce characteristic x-rays of trace elements from a variety of biologic samples. The x-ray spectra have been measured with a high resolution Si(Li) detector which can detect and separate in energy x-rays from neighboring elements with Z > 13. Tissue homogenates, frozen sections and formalin-fixed, paraffin-embedded sections of various tissues obtained from surgical and autopsy specimens have been analyzed. Measurements have been made to check the sensitivity and reproducibility of the method. Data accumulated thus far indicate that this method is useful in evaluating absolute concentration of elements usually present in a given tissue and detecting environmental elements which may have accumulated in a given tissue.