X-ray fluorescence (XRF) analysis has played an important role in elemental chemical analysis for many years. The synchrotron radiation (SR) X-ray source that has been developed in the last 10-20 years represents a revolutionary improvement in X-ray production technology. By using SR for XRF analysis, researchers can make measurements with improved sensitivity and spatial resolution.Results obtained with SR show that measurements with a spatial resolution of less than 100 ftm2 and a minimum detection limit (MDL) approaching 1 fg can be made in just 300 s. The XRF method traditionally has been used because of its multielement detection capability, minimal sample preparation, minimal damage to the sample, and ability to operate at atmospheric pressure with solid, liquid, or gaseous samples. The substitution of the SR source preserves all these attributes and opens new opportunities for exploiting the XRF method. For example, a trace element X-ray microscope can be used to