A simple HPLC method with ultraviolet detection of ciprofloxacin in human plasma was developed and validated. After protein precipitation with trichloroacetic acid, chromatographic separation of ciprofloxacin in plasma was achieved at 50℃ with a C_18 column and methanol-phosphate mixture (pH 2.5), as mobile phase. Quantitative determination was performed by ultraviolet detection at 278 nm. The method was specific and validated with a limit of quantification of 100 ng/ml. The infra- and inter-day coefficients of variation were between 1.67% and 10.55% and accuracy between 92.01% and 106.09%. The method has been successfully applied in a bioavailability study of 250 ㎎ ciprofloxacin hydrochloride tablet.