A simple and selective high-performance liquid chromatographic (HPLC) method has been developed for determination of ciprofloxacin in human gingival crevicular fluid (GCF). GCF samples were collected with paper strips. Ciprofloxacin was extracted from the pooled strips with methanol-water, 50:50 (v/v), and separated on a cartridge column (Radial-pak C 18, 100 mm x 8 mm, 10 gm) with acetonitrile-sodium dihydrogen phosphate, 2:8 (v/v), as mobile phase at a flow rate of 2 mL min(-1). The effluent was monitored with a fluorescence detector at 280 nm (excitation) and 455 nm (emission). The retention times of ciprofloxacin and internal standard quinine sulphate were 4.55 and 13.25 min, respectively. The within-day and day-to-day F recision were less than 9% for ciprofloxacin at 0.05, 0.1 and 0.4 mu g mL(-1) (n = 6), the within-day and day-to-day accuracy values were in the range 96.33-102.67% for ciprofloxacin at the concentrations given above and the detection limit corresponding to a signal-to-noise ratio of 3:1 was 3 ng mL(-1). This method was suitable and selective for determination of ciprofloxacin levels in human GCF.