The objective of the present paper is to contribute to a better understanding of the fouling phenomenon occurring during microfiltration of crude vegetable oil. To assess the role some oil components play in the fouling, the latter was monitored by the evolution of fluxes during the microfiltration of different model oils. Resistances to mass transfer were discussed to estimate the contribution of different phenomena and to compare hydrophilic and hydrophobic membrane materials. A drastic flux decline was obtained when filtering crude sunflower oil through different types of alumina membranes. Purified sunflower oil, with or without added free fatty acids, did not show any important fouling during crossflow microfiltration, suggesting that neither triglycerides nor free fatty acids are involved in the phenomenon to a large extent. By way of contrast, addition of phospholipids to the purified oil caused a drastic flux drop similar to that observed for the crude oil. The presence of small amounts of phospholipids increased the resistance to about 60 to 130% compared to that of the purified oil. The reason is most likely a fast adsorption occurring in the first instants during membrane wetting. Overall the fouling phenomenon is probably due to the fact that the phospholipids form supramolecular structures at the surface of the membrane.