A process for recovering and upgrading hydrocarbons from oil shale by contacting the oil shale solids in the presence of an acidic or oxidative catalytic substance with a water-containing fluid at a temperature in the range of from at least 705.degree. F., the critical temperature of water, to about 900.degree. F., in the absence of externally supplied hydrogen, wherein the water has a density of at least 0.15 gram per milliliter. Examples of such acidic or oxidative catalytic substance are molecular oxygen, sodium bisulfate, sodium bisulfite, and carbon dioxide.