The objective of this study was to investigate the biological treatability of a young municipal landfill leachate. The biological treatability studies were carried out under both anaerobic and aerobic conditions. In the anaerobic treatability studies, two different F/M ratios were used, the first one was 0.40 kg COD/ kg MLVSS and the second one was 1.14 kg COD/ kg MLVSS Soluble COD removal was around 95% under anaerobic conditions in each reactor and was not affected by the initial MLVSS concentrations. The third run of experiments were carried out for the determination of aerobic soluble inert COD. The initial residual COD ratio (S-10/S-0) for high strength landfill leachate was found as 0.01.