The aim of this study was to characterize hospital effluents in investigating the CHUV importance as source of pollutants, the range and amounts of pharmaceuticals that are used in the hospital and the need of source treatment of the hospital sewage. The CHUV is the biggest hospital of Lausanne (Switzerland), and 71% of its beds are in a building named “BH” (Hospital Building). The BH treats around 609 patients a day and releases an important volume of water (735 litres per patient per day), potentially highly concentrated in pharmaceuticals. The drugs the most delivered to the BH patients are the analgesic Paracetamol (787 g/day) and two anti-inflammatory substances: Ibuprofen (106 g/day) and Mefenamic acid (78 g/day). Among the 39 analysed pharmaceuticals, the most concentrated in the BH effluents are Paracetamol (423 ng/l) and Ciprofloxacin (22 ng/l). The CHUV effluents plus many other wastes from Lausanne city (homes, other health centres, etc.) are treated in Vidy wastewater treatment plant (WWTP). The treated water is then released into Lake Geneva. The load of pharmaceuticals from the CHUV was found to be relatively small, compared to the total load entering in Vidy WWTP. Maximal percentages of the WWTP inputs from the BH effluents were shown by two antibiotics: Ciprofloxacin (2.8%) and Sulfamethoxazole (4.3%). This indicates that many drugs are excreted in domestic wastewater. Although the drug levels in the water from the hospital are low compared to the total levels reaching the WWTP, they still represent a significant point source and wastewater treatment at the hospital or in the WWTP is necessary. But Vidy WWTP was shown to be particularly inefficient in treating some of the pharmaceuticals that entered it. Therefore, the risk for the environment has been assessed. Diclofenac, Ibuprofen, Paracetamol, Propranolol, Ciprofloxacin, Clarithromycin, Sulfamethoxazole and 17α-Ethinylestradiol were from 2 to 601111 times more concentrated in Vidy WWTP effluents than acceptable in terms of calculated risk quotient (RQ) values. So, in some cases, a very important risk for the environment has been demonstrated here. Improvements of the WWTP efficiency are now in progress as a response to this. Treated water leaving Vidy WWTP is further diluted (at least 84.7 times) when it enters Lake Geneva, however this study revealed detectable levels of some pharmaceuticals in the lake itself, albeit below the predicted no effect concentration (PNEC) in all cases measured in this study.