We have studied the structure of asphaltenes in heavy crude oil according to a flow chart eliminating the step of their thermal degradation and proposing separation of asphaltenes into high molecular weight components, "low molecular weight asphaltenes," and malthenes. The elemental composition of the isolated components is determined. We have used chromatography/mass spectrometry to study the composition of polycyclic aromatic hydrocarbons and heteroatomic malthene compounds contained in the asphaltenes.