Data indicate that wurtzilite is mainly alicyclic, whereas gilsonite and albertite contain more aromatic structures. However, the presence of a substantial amount of condensed aromatic systems in general structure of the bitumens is not confirmed. Generation of the gilsonite from source oil shales has resulted in significant reduction of oxygen. The changes in the character of the gilsonite and wurtzilite appear to be facies-dependent, but the difference between gilsonite and albertite is not only due to organic facies variation but also to significant diagenetic changes. All evidence suggests that expulsion of the Uinta basin bitumens, except ozocerite, has not been associated with any catagenetic changes. The strong graphitizing potential of the Uinta basin gilsonite, w rtzilite, and albertite suggests the absence or lack of thermally stable oxygen in the molecular structure of the bitumens and their source oil shales.