OZ277 is a synthetic 1,2,4-trioxolane antimalarial currently being evaluated in clinical trails. Biotransformation of OZ277 in rats results in the generation of metabolites with large differences in polarity which complicates the development of a method for the simultaneous analysis of all species. A simple, sensitive and selective hydrophilic interaction liquid chromatography-mass spectroscopy (HILIC/MS) method for simultaneous determination of OZ277 and its major metabolites in rat plasma was developed and validated. The method involves protein precipitation with acetonitrile followed by separation on a Waters Atlantis HILIC Silica column using gradient elution. The analytes were monitored using a positive electrospray ionization interface in selected ion monitoring mode. The calibration range for all of the analytes was 5-10,000ng/mL and the lower limit of quantitation was 5ng/mL using a 50microL rat plasma sample. The inter- and intra-day accuracy and precision was within 12%. The recovery of all analytes from rat plasma over a wide concentration range was 90% or greater. The method has been successfully used for quantifying OZ277 and its metabolites in plasma following intravenous administration to rats.