This study aims at identifying the effect of pretreatment such as flocculation and/or adsorption on the performance of crossflow microfiltration (CFMF). CFMF performance was studied in terms of critical flux. The results indicated that: (1) flocculation alone as a pretreatment could effectively remove the large molecular weight organic matter from 30,000 to 60,000 Daltons; (2) flocculation, together with adsorption as a pretreatment to CFMF, could remove both large and small molecular weight organics; (3) flocculation as a pretreatment was significantly better than adsorption in improving the critical flux; (4) critical flux increased from 100 L/m(2).h to 5 20 L/m(2).h when flocculation-adsorption was applied. The critical flux in long-term experiments was the same as that of the short-term experiments. However, the critical flux slightly decreased (5%) in long-term experiments compared to short-term operation with flocculation and adsorption as a pretreatment.