In the present study, we developed a fast and reliable HPLC assay for the determination of the new triazole antifungal agent voriconazole in plasma, using a Chromolith RP 18e (100 mm x 4.6 mm) monolithic silica rod HPLC column. After liquid-liquid extraction, plasma samples were separated with a mobile phase consisting of ammoniumdihydrogencarbonate buffer (pH 5.8)-acetonitrile-tetrahydrofuran (72:25:3) at a flow-rate of 3.5 mL/min and UV detection at 255 nm. The retention times for voriconazole and internal standard (UK-115794) were 2.3 and 2.7 min, respectively, and total run time was 4 min. The calibration curves were linear between 0.05 and 10 microg/mL, and within-assay and between-assay coefficients of variation were <4%. The proposed assay for voriconazole in plasma is fast, sensitive and reliable, and, thus, well suited for routine therapeutic monitoring of patients and for pharmacokinetic studies. It can be predicted that the use of monolithic silica rod chromatography will substantially shorten the turn-around time in the therapeutic drug monitoring laboratory.