Petroleum-type basic nitrogen compounds were isolated from a heavy gas oil by extraction with aqueous HCI. The resulting complex mixtures of bases was separated by fractional elution of an alumina column; the various eluates were subsequently separated by a two-step paper chromatographic technique employing toluene: methanol:water (1:10:1) and heptane saturated with methanol as developing solvents; paper electrophoresis was also utilized as a separation technique. The following compound-types were identified or their presence was indicated in the resulting fractions by various spectral techniques: quinolines, benzoquinolines, indoioand carbazoloquinolines, hydroxybenzoquinolines, 1,10-phenanthroline, and tetrahydrocarbazolenines.