The adherence of a strain ofPseudomonas aeruginosato hydrophilic contact lenses was quantitatively determined using scanning electron microscopy. Soft contact lenses were incubated for 72 h in either phosphate-buffered saline (PBS), a 500-μg/ml solution of human serum albumin (HSA), a 500-μg/ml solution of bovine submaxillary gland mucin, or a solution containing 500 μg/ml of both HSA and mucin. Lenses were then incubated for one hour in a 107-ml suspension ofP. aeruginosa.The number of adherent bacteria per field at × 8,000 magnification was determined. Only 1.96 ± 2.52 bacteria/field were found on lenses incubated in saline, whereas 5.23 ± 5.30 bacteria/ field were adherent to lenses incubated in HSA, 23.42 ± 31.01 to lenses incubated in mucin, and 26.76 ± 35.12 to lenses incubated in a solution containing both HSA and mucin. Contact lens coatings, especially mucin, facilitate the adherence off.aeruginosato soft contact lenses and may therefore play a role in the pathogenesis of contact lens-associatedpseudomonalkeratitis.