Bacterial adhesion to intraocular lenses (IOLs) during their implantation is a major etiological factor of postoperative endophthalmitis. Polypropylene was the first biomaterial that allowed this relation of cause and effect between bacterial adhesion and endophthalmitis to be proven. Adhesion to IOLs has been investigated in several in vitro studies, with contradictory results reported, due to variations in experimental conditions: the incubation times and the methods all varied. Adhesion is affected by the type of IOL, the bacterial strains, and the surrounding medium. Since this medium is very difficult to model because of its complexity, in vivo studies seemed essential. We have recently determined in vivo progression in the amount of adhering Staphylococcus epidermidis to five types of IOLs. There have been few epidemiological studies published to determine the relationship between endophthalmitis and the IOL type. However, the perfect biomaterial that could prevent postoperative endophthalmitis does not yet exist. Globally, hydrophilic materials and hydrophobic acrylic seem to be less sticky than silicone or PMMA, but this remains to be proven clinically.