Although the processability of bitumen from tar sand is dependent on its chemical composition, the details of this relationship are poorly understood. In this study, residue fractions from Athabasca bitumen (topped at different temperatures) and hydrocracker and coker residues were analyzed in detail. Separated class fractions were subjected to elemental analysis. NMR and IR spectroscopy, and potentiometrlc titration. These data were combined mathematically to obtain a structural profile of each oil. This analysis defines the structural changes in asphaltene precipitates due to distillation and processing, as well as the quantitative changes in the overall structural composition of the oil. Hydrocarbon structures such as paraffinic chains and naphthenes show definite trends with distillation and processing.