A new method for determination of ketorolac in blood or plasma samples by reversed-phase high-performance liquid chromatography has been developed. The method includes a double extraction with diethyl ether and detection by absorbance at 313 nm. Quantitation was performed by height ratios of ketorolac and the internal standard (sodium tolmetin). Detection limit of the method was 3 ng/ml using 1 ml of plasma and 10 ng/ml using 0.2 ml of blood. The method is linear in the range of concentrations typically obtained after therapeutic doses of the drug, has the advantages of using low volume of body fluid and the internal standard used is commercially available. Those characteristics allow us to conclude that this method is suitable for pharmacokinetic or drug monitoring studies.