Pharmaceuticals are applied in human and veterinary medicine and are excreted in urine and feces. The unchanged drugs or (still active) metabolites excreted by humans and animals end up in sewage and manure (Fig. 1). Unused medicines are sometimes disposed of down drains. Within the last decade, pharmaceuticals have been detected in sewage, surface water, ground water, and drinking water. This indicates that they are not fully eliminated by sewage treatment or in the aquatic environment.1-41, 2, 3, 4 We describe the occurrence, fate, and effects of pharmaceuticals in the aquatic environment.