In this paper, results of an extensive monitoring programme for pharmaceutical residues in the river Rhine are presented. For one decade (1997 until 2006), the occurrence of widely used human pharmaceuticals like analgesics, lipid regulators, antiepileptics and others has been studied at four locations along the river Rhine. The results of more than 500 analyses clearly prove that compounds such as carbamazepine or diclofenac are regularly found in the river Rhine in concentrations up to several hundred ng per litre. Combining concentration levels with data on water flow enables the calculation of transports, which e. g. for carbamazepine or diclofenac were in the range of several tons per year. The evaluation of the long-term monitoring data shows that only a slight decrease in concentration levels as well as in annual transports can be observed and thus the contamination of the river Rhine by pharmaceutical residues during the last decade has to be regarded as almost constant. Seasonal variations can be detected for bezafibrate, diclofenac and ibuprofen, for which the concentrations are much lower in the summer months. A more effective removal during wastewater treatment in the warmer periods of the year seems to be the major reason for those variations. For carbamazepine, no comparable seasonal effect can be found.