In 1999, more than 13,000 tonnes of antibacterials were used in the European Union (EU). According to an estimate by Wise, 100,000 tonnes of antibacterials may be used annually. It has been estimated that several 100,000 tonnes of pharmaceuticals are sold worldwide per year. After administration, most drugs are incompletely metabolised. For example, using data from Germany, an average excretion rate for antibacterials of 75% for the unchanged drug was calculated using amounts used and compound-specific excretion rates. Active compounds are excreted into the environment through faeces and urine. Surplus drugs not taken by patients are often disposed of down the drain or with waste. Drugs from various groups, such as cytotoxic agents, antibacterials, analgesics, spasmolytics, sedatives, x-ray and MRI contrast media and disinfectants have been detected in the terrestrial and aquatic environment throughout the world. This indicates that they are not fully eliminated, for example, by the treatment of effluent. Pharmaceuticals applied in veterinary medicine enter the environment mainly through manure and thereafter move into the soil from where they may trickle down into the ground water. As for antibacterials, not only are the compounds themselves of interest but also the input and fate of resistant bacteria. Bacteria with resistance to most antibacterials have been detected in water and soil. In a recent publication, it was suggested that resistant microbiota present in soil, in which resistance has occurred due to naturally produced antibacterials, are a major cause of antibacterial resistance in medical environments. The significance of this to the problem of the input of antibacterials into the soil is not yet known. According to the European Parliament, the use of antibacterials for growth promotion in animals has been banned in the EU from 2006. The WHO has also advised that the use of antibacterials as growth promoters should be abandoned. Prudent use of antibacterials in human medicine would not only decrease the risk of antibacterial resistance, but also help the environment. A reduction of up to 50% is supposed to be possible. (15 refs.)