An anaerobic reactor coupled with a cross-flow microfiltration unit (CFMF) was applied to treat the municipal wastewater of the Erzurum City of Turkey. Although the atmospheric conditions of Erzurum are too cold (6 degrees C average of years) to operate a big municipal wastewater treatment plant in normal operation conditions, the anaerobic membrane bioreactor system, evaluated in this study, is thought to be more useful than the conventional activated sludge wastewater treatment systems. The laboratory scale experimental unit consists of one microfiltration module of 0.2 mu m pore sized and 0.003 m(2) membrane surface area and an anaerobic reactor having a total working volume of 50 L. The maximum working volume of the reactor was kept at 15 L throughout the study. At 450 L/m(2) h, permeate flux, COD, PO4-P and suspended solids removal efficiencies were achieved as 98.1, 81 and up to 99% respectively. Our anaerobic membrane bioreactor system displayed a good performance to remove carbonaccous and phosphorous materials. Furthermore, suspended sludge and sludge microorganism concentrations were under the detectable levels in the effluent of the system.