PURPOSE: To report a clinical series of ciprofloxacin-resistant ocular isolates of Pseudomonas aeruginosa from a tertiary care ophthalmic center, METHODS: Review of in vitro sensitivities of all ocular isolates of P, aeruginosa between July 1991 and September 1998, In vitro resistance was defined as a minimum inhibitory concentration of 4 or more mu g per mi, RESULTS: Nine of 423 ocular isolates of P, aeruginosa showed in vitro resistance to ciprofloxacin. From 1991 to 1994, 0.44% (1/227) of ocular isolates were resistant to ciprofloxacin, whereas from 1995 to 1998, 4.1% (8/196) of ocular isolates showed in vitro resistance (P = .014). CONCLUSIONS: Ciprofloxacin-resistant P, aeruginosa has been identified in recent clinical ocular specimens. Ciprofloxacin resistance among ocular isolates of P, aeruginosa is a local and worldwide concern. (Am J Ophthalmol 1999;128:509-510. (C) 1999 by Elsevier Science Inc. All rights reserved.).