The applicability of slurry-based (semi-liquids) BMP assay in determining biodegradation kinetic parameters of landfilled waste is critically reviewed. Factors affecting the amount and rate of methane (CH4) production during anaerobic degradation of municipal solid waste (MSW) and optimal values of these factors specific to landfill conditions are presented. The history of conventional BMP, and some existing procedures are reviewed. A landfill BMP (LBMP) assay is proposed that manipulates some of the key factors, such as moisture content, particle and sample size, that affects the rate of CH4 production and the CH4 generation potential of landfilled MSW (LMSW). By selecting proper conditions for these factors, a representative BMP assay could be conducted to ensure accurate determinations of CH4 potential and the kinetic parameters k; first order rate coefficient and L-o; methane generation potential.