Seven homologous series of alkylbenzenes ranging in carbon numbers from approximately C10 to C35 have been tentatively identified in United States Tertiary, Cretaceous, and Carboniferous coals. The assigned alkylbenzene structures were deduced in the light of selective microbial and geothermal degradation of carotenoids. Possible significance of the relative concentrations of the alkylbenzene homologs is discussed.