Annual total metal and metalloid inputs on agricultural lands via poultry litter amendments are not regulated at either the federal or state levels at this time, and the effect that continuous poultry litter amendments have on As contamination in Mid-Atlantic soil and water environments is not known. The source of the As in the poultry litter is an organic acid, hydroxyphenl-arsonic acid, Roxarsone, which is fed to poultry to control coccidiosis disease, to enhance growth, and to improve feed conversion. Through a number of biological and mineralogical processes, it is thought, based on solution speciation analyses, that the As in Roxarsone is converted to the more toxic inorganic forms, As(V) and As(III). To glean more precise information on the chemistry and speciation of As in the poultry litter over time, a controlled poultry house study was conducted. Feed and litter samples were examined over the life cycle of a flock of broilers. A series of starter and control feeds were fed to the birds. Arsenic concentrations in the feed were 2.7, 12.7, and 0.56 mg kg-1, respectively. The poultry litter had total As levels ranging from 8-25 mg kg -1. Water soluble As data are consistent with earlier studies and show that more than 50% of the As in the litter is water soluble. In order to determine the direct speciation of the As in the poultry litter over time, X-Ray Absorption Near Edge Structure Spectroscopy (XANES) and X-Ray Fluorescence (XRF) mapping were performed at the Advanced Light Source (ALS) in Berkeley, CA and the National Synchrotron Light Source (NSLS) in Upton, NY. The data revealed that As (III) and As(V) are the main species of As in the poultry litter , supporting the earlier solution speciation data showing that Roxarsone appears to be transformed to more toxic, inorganic forms. However this transformation appears to occur more rapidly than was first assumed.