This article addresses adsorption phenomena in UF membrane filtration within the context of some organic matter encountered in drinking water treatment. Both the intensity of the adsorption and its impact on the flux are considered. Then, two types of pretreatment and their effect on membrane fouling reduction are evaluated. One pretreatment, preozonation, was evaluated in terms of the effect on the organic compounds' nature and their interactions with the membranes material. The second pretreatment evaluated was preadsorption on powder activated carbon (PAC), which was expected to act competitively with the membrane in terms of adsorption. The products, which otherwise would adsorb on the membrane and foul it, would preferably adsorb on the PAC and therefore membrane fouling would be prevented.