Se localilzation in the human oral mucosae which contain dental amalgam or dental silver alloy particles was analyzed by X-ray scanning analytical microscopy (XSAM). Se distribution was visualized, and the localization in the neighbor of amalgam or silver particles was confirmed. The chemical state of Se was analyzed by X-ray absorption fine structure (XAFS) analysis. Se was estimated as the low valency state. The possibility of using XSAM and XAFS for the analysis of the distribution and chemical state of rarely contained elements in biological tissue was Suggested.