A high-performance liquid chromatographic method for the simultaneous determination of ofloxacin, norfloxacin and ciprofloxacin in human hair is described. A reversed-phase C18 column and a fluorescence detector with switching fluorescence wavelengths were used together with solid-phase extraction of the drugs from hair dissolved in 1 M sodium hydroxide. Reproducibility and linearity studies yielded coefficients of variation of 0.2-2.2, 1.4-3.1 and 1.5-3.4%, and correlation coefficients of 1.000, 0.999 and 0.999 within the concentration range 0.3-100 ng/ml for ofloxacin, norfloxacin and ciprofloxacin, respectively. For validation, hair samples were obtained from six subjects who had been taking one or two of the three fluoroquinolones. Assuming a hair growth-rate of 1 cm per month fluoroquinolones could be detected in the hair section(s) that had grown approximately between the dates of drug administration and hair sampling.