Drugs are emitted into the environment by hospitals, private households, veterinary and human practices. Remnants of these products are primarily disposed of in landfill sites. At the present, there is no information available about the behaviour of pharmaceutical drugs, like their anaerobic biodegradation or adsorption, in sanitary landfills. Some of these drugs, e.g. antineoplastic substances such as ifosfamide, are supposed to be cancerogenic, mutagenic, fetotoxic or embryotoxic. Therefore, we investigated the behaviour of ifosfamide during waste decomposition in a laboratory-scale lysimeter. Up to 50% of the ifosfamide was eliminated under methanogenic conditions; but the mechanism applying for the elimination remains unclear. As far as present day knowledge is concerned, the risk for the environment through the emission of emitting ifosfamide from sanitary landfills should be negligible.