The autoxidation of branched alkanes, pristane (2,6,10,14-tetramethylpentadecane) and squalane (2,6,10,15,19,23-hexamethyltetracosane), has been studied in the liquid phase at 170 degrees C with products identified by CG-MS and quantified by GC-FID and chemical mechanisms for their formation proposed. For pristine, the relative rate of radical attack on tertiary hydrogen atoms was measured to be 15 +/- 1 times faster than attack on secondary hydrogen atoms, with 16 of the 23 products identified formed by the further reaction of tertiary alkoxyl radicals. Tertiary alcohols are the most significant product (29 +/- 4% of reacted pristane early in the reaction), while most smaller products can be accounted for by fragmentation of tertiary alkoxyl radicals of pristane (55 +/- 10% of reacted pristane early in the reaction). These fragment products include alkanes, formed by the reaction of 27 +/- 3% of primary alkyl radicals abstracting hydrogen atoms instead of adding oxygen molecules.