A gas chromatography-mass spectrometry (GC-MS) method for determination of ketone bodies (ß-hydroxybutyrate, acetone, and acetoacetate) in blood is presented. The method is based on enzymatic oxidation of D-ß-hydroxybutyrate to acetoacetate, followed by decarboxylation to acetone, which was quantified by the use of headspace GC-MS using acetone-(13)C(3) as an internal standard. The developed method was found to have intra- and total interday relative standard deviations <10% for acetone+acetoacetate levels (~25 to 8300 µM) and D-ß-hydroxybutyrate levels (~30 to 16500 µM). Recovery values varied from 98 to 107%, demonstrating the suitability of the method for measuring ketone bodies over a wide concentration range. The method has been applied to cases in which ketoacidosis was suspected as the cause of death in diabetics or chronic alcoholics, as well as to cases in which another cause of death was identified.