This 2003 Annual Report describes the research and accomplishments of staff and users of the W.R. Wiley Environmental Molecular Sciences Laboratory (EMSL), located in Richland, Washington. EMSL is a multidisciplinary, national scientific user facility and research organization, operated by Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy's Office of Biological and Environmental Research. The resources and opportunities within the facility are an outgrowth of the U.S. Department of Energy's (DOE) commitment to fundamental research for understanding and resolving environmental and other critical scientific issues.