In Europe, a variety of prescription and non-prescription drugs have been identified in the effluents of sewage treatment plants (STPs) and in rivers and streams near discharges from STPs. Chronic exposure of aquatic organisms to drugs in surface waters could induce biological effects that may alter their physiology, behavior or reproductive capacity. The primary objective of this project was to evaluate the occurrence and concentrations of prescription and non-prescription drugs in the Canadian aquatic environment, including the effluents from domestic sewage treatment plants (STPs) and surface waters near STP discharges.