The absorption of a single oral dose of ciprofloxacin 750 mg in patients with cancer who had chemotherapy-induced Cancer and Leukemia Group B grade I or II mucositis was evaluated. Ciprofloxacin was administered after an overnight fast. Plasma samples were collected before and 0.5, 1, 1.5, 2, 3, 4, 6, 8, and 12 hours after the dose. Drug concentrations were determined by reverse-phase high-performance liquid chromatography with fluorescence detection. Pharmacokinetic values were characterized by noncompartmental methods. The mean +/- SD for area under the curve, mean peak concentration (C(max)), and time to C(max) (T(max)) were 18.7 +/- 5.03 mg/L x hour, 4.41 +/- 1.74 mg/L, and 1.81 +/- 0.843 hours, respectively. The absorption of oral ciprofloxacin in patients with chemotherapy-induced grade I or II mucositis compares with that in healthy volunteers. These findings may call for further pharmacokinetic evaluation of the drug in a similar patient population.