It was shown that the complete hydrocarbon-type composition of natural hydrocarbon systems can be determined by means of the low-voltage mass spectrometric analysis of oils obtained via the deresining of crude oils and the group concentrations of hydrocarbons of 30 structural types can be measured in these systems if the previously revealed characteristics of the molecular- mass distribution of hydrocarbons of different classes in crude oils are taken into account. The results of such an analysis of more than 40 different-type oils and natural bitumens from different oilfields and oil-bearing provinces of Eurasia are discussed. The obtained mass spectrometric data formed the basis for a new approach to the chemical typification of oils in which the hydrocarbon composition of the test object as a whole-not its separate (usually, small) portion-is characterized, in contrast to most previous traditional methods of classification.