Abstract: A process for the preparation of a modified aromatic hydrocarbon resin which comprises reacting an aromatic hydrocarbon-formaldehyde resin with an unsaturated polybasic acid or an anhydride thereof, together with a saturated polybasic acid or an anhydride thereof if necessary, in the presence or absence of water, while introducing steam into the reaction system to remove by-produced formaldehyde out of the reaction system, and reacting the formed reaction product with at least one dihydroxy compound selected from the group consisting of (A) a glycol and (B) a hydroxy-terminated oligomer obtained by reacting a glycol with an unsaturated polybasic acid or an anhydride thereof; the cured product of the modified aromatic hydrocarbon resin being excellent in mechanical strength and resistance to water and alkalis.