Aromatic hydrocarbons produced from the reaction of Green River oil shale with carbon monoxide and water at elevated pressure and at temperatures from 300 to 450/sup 0/C were investigated. The isolation of these aromatic hydrocarbons involved ion exchange, complexation, silica gel, and alumina chromatographic techniques. Compound types present in these aromatic hydrocarbons were studied by high resolution mass spectrometry and combined gas chromatography-mass spectrometry. Compound types were mostly phenylcyclohexylalkanes, dinaphthenobenzenes, trinaphthenobenzenes, naphthenonaphthalenes, and carotenoid types at 300/sup 0/C; but at 450/sup 0/C compound types were mostly alkylbenzenes, alkylbiphenyls, and alkylnaphthalenes. The composition of aromatic hydrocarbons from the benzene-extracted bitumen of Green River oil shale was found to be similar to that in the 300/sup 0/C product from the CO-H/sub 2/O reaction.