Purpose.To compare the adherence ofAcanthamoebatrophozoites and cysts to two types of unworn conventional and disposable contact lenses included in groups 1 and 4 of the Food and Drug Administration and to assess the adherence to the center and edge of the lenses.Methods.We used 10 conventional and 10 disposable contact lenses belonging to groups 1 and 4 of the Food and Drug Administration. Each lens was divided into four segments. A human corneal isolate ofAcanthamoebasuspended in saline (1× 105 amoebae/mL) was used. Lens segments were exposed toAcanthamoebacysts and trophozoites for 2 hours. After removal, the count was made with an optical microscope at 100× magnification. Three fields at the center and three fields at the edge were read on each segment.Results.Acanthamoebaadhered to both types of contact lenses, with a proportion of trophozoites to cysts between 6:4 and 7:3. There was a significantly higher adherence to disposable (8.14 ± 3.57 organisms/mm2) than to conventional (4.94 ± 2.33 organisms/mm2) (p< 0.0001) contact lenses. We also found that the greatest adherence was to the edge of the conventional (12.05 ± 4.03 organisms/mm2) and disposable (26.10 ± 7.84 organisms/mm2) (p< 0.0001) contact lenses.Conclusions.This study shows thatAcanthamoebahas varying adherence affinity for different new hydrogel contact lenses. The affinity for disposable lenses (etafilcon A) is significantly higher than that for conventional lenses (polymacon). This adherence is greater for ionic material and high water content. The use of low water content, nonionic contact lenses may reduce the adherence ofAcanthamoeba. Finally, the edge may play an important role as anAcanthamoebavector.