The review catalogs the process research in direct thermochemical conversion of biomass to liquid hydrocarbons fuels. Subject areas include pyrolysis, high-pressure liquefaction, upgrading of both pyrolysates and high-pressure oils, supporting analytical and basic research, and technoeconomic assessments. Much progress is presented for the time period from 1983 to 1990. The pyrolytic processes with lower investment costs and higher yields of more oxygenated oils are moving more quickly forward in development. Further development is still required for the upgrading processes for the production of hydrocarbons from the primary oils. Based on these developments, potential exists for economical production of substitute liquid hydrocarbon fuels and chemicals from biomass.