Model dihydroaromatic compounds (0.021 M and 0.123 M) and Safaniya petroleum bitumen (ca. 0.021 M) in toluene and Decalin solution at 50.0 degreesC were oxidized with air for up to 500 h in the dark. The rate of oxygen uptake was measured by gas chromatography using a column packed with molecular sieve 5A at 70 degreesC. The model compounds showed a slow linear rate of oxidation with an induction period apparent in some cases. In contrast the bitumen showed no induction period and the typical rapid initial rate of reaction becoming linear at longer times (>100 h) was observed. Oxidation of the most reactive of the model compounds (9,10-dihydroanthracene) was inhibited by 2,4-di-tert-butyl-4-methylphenol whereas the reaction of bitumen was unaffected. Bitumen and DHA did not act synergistically to increase the overall rate of oxygen uptake (compared to the sum of the individual reactions) when co-oxidized in toluene. Bitumen (4 g, ca. 0.0064 mols) hydrogenation with o-chloranil (0.203 g, 0.00082 mel) in refluxing toluene and Decalin (110 degreesC and 160 degreesC, respectively) for up to 24 h indicated the presence of a dihydroaromatic group concentration of about 3 x 10(-5) to 7 x 10(-5) mol per gram of bitumen. However, removal of these groups through hydrogenation had no significant effect on the rate of oxygen uptake of bitumen solutions. Both model compound studies and hydrogenation experiments indicate that dihydroaromatic species may not be significant in the primary oxygen uptake process of bitumen oxidation.