The objective of this experimental run was to test the biodegradability and the ability to treat through composting of an autoclaved MSW at 130 °C. The waste (Floc MSW 130) was tested alone and also mixed with seeding materials: pig slurry and liquid sludge, in order to study the effect of seeding. Respirometric measurements and pilot composting trials were run with the three mixtures.Through the modelling of the respirometric measurement, we determined that the autoclaved MSW organic matter contained 43% of biodegradable organic matter. This biodegradable organic matter was essentially composed of slowly biodegradable compounds (94 %) that have to be hydrolysed before being used by the micro-organisms. The composting of the autoclaved waste led to important mass losses: about 30 % of the dry mass and 49 % of the organic matter mass. Only 20 % of the nitrogen content was lost during the treatment. Temperatures reached during composting were in agreement with a good hygienization of the waste.The effect of the seeding of the material was study by measuring the respirometric activity and by composting the autoclaved waste with a pig slurry and a liquid sewage sludge. Any significant effect of the seeding was observed neither through respirometric measurement, nor through composting.