A major limitation to assessing the health related impact of environmental arsenic (As) is the inadequacy of current analytical methods, especially in regards to providing speciation information of environmental As compounds. The lack of information on speciation is problematic as it is well known that different As species have considerable differences in bioavailability, toxicity and presumably in carcinogenicity. The primary objective of this project is to develop analytical procedures suitable for characterizing and speciating low levels of As in drinking water and biological fluid samples. Ultra sensitive laser induced fluorescence (LIF) approaches will be developed to measure ultra trace levels of As in various sample matrices. These studies will establish the efficacy of the LIF approach and demonstrate its utility for characterizing very low levels of As species in a variety of sample materials.