In this study, the treatability of raw and anaerobically pre-treated domestic sewage in sequencing batch reactor systems was compared. In this context, two sequencing batch reactors, the first one (SBR1) fed with raw domestic sewage and the second one (SBR2) fed with anaerobically pre-treated domestic sewage, were operated at six cycles per day operation. The feeding was introduced into the reactor by pumping for 30 min (the last 15 min with mixing), mixed and aerated for 180 min, followed by 20 min of settling. The effluent COD concentrations of SBRs were 5070 mgL(-1). The effluent orthophosphate concentrations of SBR 1 and SBR 2 were 4-1.5 mgL(-1) and 5.5-3 mgL(-1), respectively. Experimental results showed that in both SBR1 and SBR 2 the removal efficiency of NH4-N was about 100%, and nitrification rates in SBR1 and SBR2 were 12.2 mg g(-1) VSS h(-1) and 21.8 mg g(-1) VSS h(-1), respectively.