In 1998 the Institute for Sustainable Waste Management and Technology (IAE) assigned the construction of the Model Landfill Allerheiligen. The aim of the project was to investigate the behaviour of mechanical-biologically pre-treated (MBT) household waste under landfill conditions. The tasks of IAE additionally consisted on the scientific follow-up of the pilot project by investigating the long-term behaviour of the MBT-waste. Four closed large-scale lysimeters with a 5 m x 5 m basis and a height of 3 m were constructed for the experiments nearby the landfill Allerheiligen. The lysimeter-cells were filled with pre-treated waste material (<12 mm) from the MBT-plant. The waste was then covered with a 5 m layer of compost material in order to minimise the influence of the ambient temperature. Different moisture conditions were examined during the experiment: two test-cells were irrigated with fresh water and with the collected leachate (wet conditions). The other two test-cells were operated without irrigation (dry conditions). The amount and quality of the produced gas and leachate was measured during the experiment. The chemical analyses of the leachate were performed continuously, with the exception of the time period from springtime 2000 until autumn 2001, when no measurements were carried out. In summer 2003, at the end of the five-year-experiment, the cells 1 and 2 were opened and the remaining material was c