Published data on C-22, C-26, and C-30 higher petroleum polymantanes and their methyl-substituted homologues are summarized. Problems of the thermodynamic stability of the isomers and possible routes of the formation of these hydrocarbons in nature are considered and discussed. Special attention is given to the description of modern investigation techniques using computerized GC-MS systems with recording characteristic base ions: M+ for bare-ring structures and M+-15 for methyl-substituted hydrocarbons.