Abstract: A modified coal tar useful in roofing applications, containing coal tar, a nitrile butadiene rubber, and in some instances an effective amount of a plasticizer is prepared by heating the coal tar to a molten temperature, adding the rubber in powder form and agitating the material in a suitable high shear mixing apparatus until adequate phase inversion occurs between the polymer and the coal tar phase. After preparation, the material is cooled in containers until use, at which time it is heated to a flowable temperature and applied using a roofing mop or squeegee. Effective plasticizers include the alkyl esters of di-functional carboxylic acids, such as di-octyl adipate and di-octyl phthalate.