This study evaluates the impacts of three different pretreatment methods on the biogas production from sugar beet, when it is anaerobically digested with a variety of inoculum mixing ratios. In this context, this research focuses on the influences of different pretreatment methods and inoculum on the digestibility on the digestibility. Sugar beet was anaerobically digested at 37°C. Actively digested cow manure slurry, vegetable and fruit residues mix was used as inoculum. The series of laboratory experiments using 32 digesters (each 1 L) were performed in batch operation mode. The results prove that inoculum and pretreatments could either enhance the biogas potential or totally inhibit the digestion. Key words: sugar beet, inoculum, pretreatment methods, biogas production.