Bacterial viability in bacterial adherence to new soft contact lenses (SCLs) was studied by exposing polymacon and lidofilcon A lenses toPseudomonas aeruginosa:L, live, untreated bacteria; H, bacteria heated for 1 h at 100°C; and P, bacteria treated with 3% hydrogen peroxide for 1 h. Cultures of groups L, H, and P showed heavy, no, and minimal bacterial growth, respectively. Scanning electron microscopy (SEM) showed significantly less bacteria on new SCLs in groups H and P. Transmission electron microscopy (TEM) showed that bacterial shape was mostly preserved in all groups, with marked intracel-lular and cell membrane changes and breaks (groups H and P), margination of intracellular electron-dense material (group H), and central and peripheral vacuolation (group P). Adherence to new SCLs appears to be an active process, as killed or altered bacteria adhere less.