Photodecomposition of aliphatic alcohols and liquid paraffins sensitized by asphaltenes and resins of heavy pyrolysis tar (HPT > 400 degrees C) was studied by ESR and low-temperature photolysis. It was shown that the photoirradiation of frozen solutions of asphaltenes and resins in alcohols and paraffins generated alcohol and hydrocarbon radicals. The photosensitizing properties of resin-asphaltene compounds was found to facilitate the photodegradation of organic compounds via both one- and two-photon mechanisms with a more efficient use of solar energy.