□ A simple, reversed phase high performance liquid chromatographic method has been developed for the determination of ribavirin, silybin, interferonα2a, lamivudine, and ursodeoxycholic acid in pharmaceutical preparations, human plasma, and urine. The method was conducted using A Shim-pack VP-ODS (150×4.6 mm i.d) stainless steel column at ambient temperature with ultraviolet (UV) detection at 214 nm. Micellar mobile phase is consisting of of 0.1 M sodium dodecyl sulphate, 8%n-propanol, 0.3%triethylamine in 0.02 M phosphoric acid (pH 6.0) was used and it was pumped at a flow rate of 0.8 mL/min. The calibration curve was rectilinear over the concentration range of 0.01–0.1μg/mL, 0.01–0.2 µg/mL, 0.1–1.0 µg/mL, 0.05–1.0 µg/mL, and 0.01–0.5 µg/mL for ribavirin, silybin, interferonα2a, lamivudine, and ursodeoxycholic acid, respectively. The proposed method was successfully applied to the analysis of these drugs in some dosage forms. The method was extended to the in vitro, in vivo determination of these drugs in spiked human plasma samples with the mean%recoveries of 99.17 ± 1.10, 99.10 ± 0.88, 98.9 ± 0.80, and 99.10 ± 0.88 for ribavirin, silybin, lamivudine, and ursodeoxycholic acid, respectively.