Cross-fuse filtration experiments were performed using three model biofoulants with increasing complexity: a monospecies assay using Pseudomonas aeruginosa or Escherichia coil, a duospecies assay using both microorganisms, and finally a multispecies assay using activated sludge spiked with P. aeruginosa. Three different microriltration membranes were tested: polyvinyldifluoride, polyethylene and polysullone. The biolouling was characterized in terms of cell density, community composition and relative permeability decrease caused by the different bioloulants. The data show that a good biofilm pioneer, like P. aeruginosa, was able to bind to any kind of membrane. However, when activated sludge spiked with P. aeruginosa was used, an enhanced biolouling behavior by the activated sludge members was found on the polyvinyldifluoride membrane. This paper highlights the importance of the kind of species, the microbial interactions and the community composition during the biofouling development. (C) 2013 Elsevier B.V. All rights reserved.