In this paper, we present laser light reflectometry [1] (not to be mistaken with ultrasound reflectometry [2] that uses ultrasound waves) as a tool for quantitative investigation of (the initial stages of) fouling on membrane-like surfaces. Reflectometry allows in situ investigation of adsorption and accumulation of components near a surface However, before the method can be applied, a membrane-resembling layer should be attached to a reflecting surface and this layer should have minimal roughness. This was investigated for the widely used membrane materials polyethersulfone (PES), polyvinylpyrrolidone (PVP), and a blend of both The adsorption of typical foulants, such as BSA, dextrin, and tannin was followed in time Both unmodified and modified surfaces, obtained through pre-adsorption of Tween components were investigated The interactions responsible for adsorption of foulants could be charted, and surface modifications could be proposed that specifically target these interactions (C) 2010 Elsevier B.V All rights reserved