The anaerobic digestion of leachates from a solid urban wastes landfill was studied using an upflow anaerobic sludge blanket reactor in pilot scale. The strategy of start-up and acclimation was based on gradual substitution of easily biodegradable feed with landfill leachate. All modifications were based on the attainment of 70% COD removal. Having completed the start-up, the kinetics of leachate biodegradation were studied and the values of kinetic parameters were obtained by fitting experimental data to the equation of Chen and Hashimoto. The biodegradability assays indicated that 40-50% of COD in leachate was biodegradable. The highest COD removal was 90-100% if only the biodegradable matter was considered.