The present paper describes an approach to structural analysis of petroleum products based on proton n.m.r. spectroscopy The following changes have been found to occur on thermal oxidation of asphaltic feeds aimed at production of paving grade bitumens: the yield of asphaltenes, their molecular mass, f(a), (H/C)aru and oxygen content increase, while K(ar), sigma and R(a)e decrease. The changes in both gudron feed types proceed in the same direction, the basic tendency being the formation of considerable quantities of asphaltenes with high degree of aromaticity, but smaller size of the structural units. In the process of thermal oxidation the amount of resins decreases in both raw materials, different alterations being observed however. The oil fractions undergo similar changes, more favourable in the Russian type paving grade bitumens which exhibit a more pronounced aromatic character. The paving grade bitumen with physico-chemical performance meeting the standard requirements is characterized by a high degree of similarity between the ＇＇structural units＇＇ building the oil, resins and asphaltene components.