This study was conducted to understand fouling formation and effect of PAC addition in a hollow-fiber ultrafiltration membrane integrated with adsorption. Daily carbon accumulation rate and carbon mass load to UF module were estimated to be about 10 mg/L and 117 g/m(2.)d, respectively, however carbon build-up within the PAC-UF membrane was not so significant during 76 days operation and was locally limited to inlet and outlet of module, which were vertical to direction of linear velocity. Carbon addition had scouring effect on large particles and could prevent particles larger than 6 mu m from depositing on the hollow fibers. Organic amount extracted from the PAC-UF was almost half that from the UF, due to reduction of organic load by carbon adsorption. PAC addition also imparted an entrapping effect on metal ions within PAC, however PAC remained from incomplete backwash increased amount of inorganic foulant extracted from the PAC-UF. Reversible resistance by particles and carbons was the greatest by 54% of total reversible resistance, followed by inorganic (33%) and organic foulants (13%). More deliberate strategies such as sufficient backwashing pressure, greater linear velocity, feed water direction and module design can be expected to alleviate cake formation through this investigation.