A novel solid-phase extraction and a robust high-performance liquid chromatographic (HPLC) separation procedure for artesunate and alpha- and beta-dihydroartemisinin, using post-column alkali decomposition and UV detection is described. Extraction was performed with Bond-Elut Phenyl solid-phase extraction cartridges and analysis by HPLC was carried out using a Waters Symmetry C8 5-microns 150 x 3.9 mm I.D. column. The mobile phase was 50% acetonitrile in 0.1 M acetate buffer (pH 4.8) delivered at a flow-rate of 0.7 ml/min. The column eluate was mixed with 1.2 M potassium hydroxide in 90% methanol delivered at 0.3 ml/min, in a 1-ml reaction coil at 69 degrees C, to form UV-absorbing chromophores which were detected at 290 nm. The recovery of all analytes was greater than 80%. There was no significant difference in the peak-area ratio of alpha- and beta-dihydroartemisinin in plasma. Preliminary pharmacokinetic data from six adult Vietnamese patients who received 120 mg of artesunate by intravenous injection for the treatment of acute falciparum malaria are presented. Despite limited data, the mean half-life of artesunate was approximately 3.5 min while that for dihydroartemisinin was 34 min. These data confirm the relatively rapid clearance of both artesunate and its principle active metabolite, dihydroartemisinin.