Human, wildlife and regulatory concerns prompted this study into the factors that affect the accumulation of methylmercury (MeHg) in fish in Maryland lakes and reservoirs. The Maryland Department of the Environment (MDE) issued fish consumption advisories for all freshwater lakes in Maryland in December, 2001. Maryland watersheds receive elevated rates of mercury (Hg) deposition, and deposition rates appear to vary substantially across the state. Watersheds across the state also have different abilities to convert inorganic mercury into MeHg, the form that accumulates in food webs. Some of these factors may be controllable through emissions regulations, or by reservoir or land use management. The overall study objective is to provide the state of Maryland with information to aid in management of MeHg bioaccumulation in fish in Maryland reservoirs.