Abstract: A hydropyrolysis process for upgrading heavy, high molecular weight feedstocks such as coal-derived liquids, petroleum crudes, tar sand bitumens, shale oils, bottom residues from process streams, and the like, to lighter, lower molecular weight liquid products. The process includes subjecting the feedstocks to pyrolysis in the presence of hydrogen under carefully controlled conditions of temperature and pressure. The process can be defined as hydrogen-modified, thermal cracking in the specific temperature range of 450.degree. C. to 650.degree. C. and in the hydrogen pressure range of about 120 psi to 2250 psi. The amount of hydrogen present can be varied according to the type of feedstock and the liquid product desired. Although the hydrogen is not consumed in large amounts, it does participate in and modifies the process, and thereby provides a means of controlling the process as to the molecular weight range and structural type distribution of the liquid products.