The influence of different types of surfactants on two types of microfiltration membranes was investigated for different pore sizes and membrane usage. The surfactants were an anionic (sodium lauryl sulphate) surfactant and two non-ionic surfactants of which one [poly(ethylene glyco1)2025] has an inverted cloud point. The other was polyoxyethylene sorbitan monooleate (Tween 80). The chosen microfiltration membranes are commercially available Ceramesh and PVDF [poly (vinylidene fluoride)]. The flux reductions were found to be more pronounced with the latter which is hydrophobic. Below the cloud point the minimum reduction was 20% for the hydrophobic membrane. New and cleaned membranes were studied, the reductions being greater in the former case. Overall the flux reductions were as significant as those found previously for hydrophobic ultrafiltration membranes.