Resumen del autor, extraido del trabajo. Generation of gaseous hydrocarbon from humic coals has long been accepted by petroleum geologists while generation of liquid hydrocarbon in commercial quantity from coal is still a matter of debate. In present study an attempt has been made to evaluate the quantity of liquid hydrocarbon generated and expelled from coaly Shemshak Formation, NE Iran. The Shemshak Formation is extensively distributed in Eastern Alborz region ranging in thickness from 1500m to more than 2000m. It consist of shale, sandstone and conglomerate interbedded with several coal layers of various thickness. Based on the petrographic studies of various coal layers it was inferred that considerable amount of oil prone liptinitic organic matter are associated with these layers. Vitrinite reflectance values varies from 0.7 to1.5% indicating catagenetic stage of thermal maturation corresponding to oil generation window. This is further supported by reliable Tmax values. Amount and nature of hydrocarbon generated were determined using initial petroleum potential, petroleum generation index, petroleum expulsion efficiency, coal density, effective thickness and areal distribution of coal layers. Petroleum potential varies from 0.07 to 69.4 mgHC/g rock indicating high potentiality of these layers to generate liquid hydrocarbon. Petroleum expulsion efficiency and petroleum generation index vary from 0.08 to1 and 0.01 to 0.08 respectively. Considering the large areal extent and great thickness of Shemshak Formation together with thermal maturation of organic matter it was concluded that commercial quantity of liquid hydrocarbon has been generated from this formation.