Among 385 specimens of presumed microbial keratitis cultured at Beijing Institute of Ophthalmology from April 1988 to December 1990, 21(6%) were associated with extended-wear contact lenses. Of the latter, 10(48%) were cultured bacterio-positive, including 8(80%) of gram-negative and 2(20%) of gram-positive bacteria. Pseudomonas aeruginosa was found in 6 specimens, accounting for 60% of the bacterio-positive cultures. In the meantime, among the 364 specimens not associated with contact lens wear, 87(24%) were cultured positive, including 27(31%) of gram-negative bacteria, 32(37%) of gram-positive bacteria and 20(23%) of fungi, while mixed cultures and nocardia each accounted for 4(5%). 9 contact lens containers and all cleaning solutions of 11 cases of pseudomonas corneal ulcers were cultured to find them 100% positive of P. aeruginosa.