A high-performance liquid chromatographic method with fluorimetric detection is described for the routine and selective determination of taurine in urine, serum, tissues and isolated hepatocytes. The preparation and use of ion-exchange resins to extract taurine from biological samples is included. Taurine was derivatised with o-phthalaldehyde/2-mercaptoethanol prior to injection onto a C18 column (LiChrospherR 100 RP-18, 5 microns, 125 x 4 mm I.D.). Isocratic elution of the adduct was carried out using NaH2PO4 (0.05 M, pH 5.4) in methanol and water (43:57, v/v). Homoserine was used as an internal standard to facilitate the standardisation and quantitation of samples and analysis was completed in 6 min with homoserine and taurine eluting after 3 and 4 min, respectively. The method will detect 0.5 pmol of taurine on the column. Appropriate dilutions of these biological samples enable these samples to be assayed on an autosampler, using the same standard curve. Concentrations of taurine in human, dog and rat urine, rat liver, serum and isolated hepatocytes are reported.