Continued investigation of the new technique of ion microscopy is proposed for the intracellular elemental and isotopic cytochemical analysis of biological specimens. The proposed methodological and instrumental improvements would enhance the applicability of ion microscopy to biomedical research related to understanding the role of elements in the state of health and disease. Methodological improvements include characterization of the frozen-hydrated biological matrix, quantification of ion images from freeze-dried biological specimens using internal and external standards and digital image processing, and subcellular localization of ion transport and biomolecules using stable isotopes as tracers. Improved spatial resolution capabilities of ion microscopy in the nanometer range will be applied to biomedical research. A number of fundamental and applied collaborative studies are proposed representing a broad scope of biomedical areas. In collaboration with researchers at NIH, subcellular localization of copper in human skin fibroblasts from patients with Wilson's disease will be investigated. The knowledge of cellular stores of copper and their redistribution under diseased state would help resolve some of the basic questions in copper metabolism and provide a better understanding of the disease. The combination of ion and fluorescence microscopy will be explored for understanding the complex role of calcium in the secretory response of mast cells. In collaboration with researchers at Cornell, ion microscopy will be utilized in understanding the intestinal absorption of calcium and lead- calcium interactions at the cellular level. The ion imaging and isotopic capabilities of the ion microscope are well suited to investigate the absorption and transport of this important ion. Additional biomedical application will be explored as time and experience permits.