The implementation of low-cost, simple mitigation measures is required for the timely control and sustainable management of pollution problems in developing countries. Recently, the use of anaerobic systems for wastewater treatment has received a growing attention since they represent an alternative cost-effective approach for removal of pollutants. Therefore, evaluation of the performance of an Upflow Anaerobic Sludge Blanket Reactor, as a pre-treatment step for industrial as well as domestic wastewater was the subject of this study. The results obtained showed that the performance of one-stage UASB at 8hrs hydraulic retention time (HRT) for domestic wastewater treatment was quite satisfactory. CODtot and BODtot removal values averaged 77% and 83%. Comparison of the performance of a one-stage versus two-stage reactor, having the same volume and operated at the same HRT (8 hr) and biomass concentration indicated an improvement in the quality of the two-stage effluent. With regard to the wastewater discharged from a potato-chips factory, the use of one-stage UASB at a detention time of 18hrs and an average organic load of 2.9 kg BOD/m3/d gave good results. Average residual values of COD, BOD, TSS and oil and grease in the treated effluent were 650, 342, 203 and 63 mg/l, respectively. Operation of a two-stage pilot-scale UASB indicated better performance as expressed by COD and BOD removal values.