Abstract: A method for inhibiting polymer build-up in a recycle line and a heat exchanger during a polymerization process of one or more alpha olefins, particularly sticky polymers, or of one or more diolefins such as butadiene, isoprene, styrene, or styrene and butadiene which method comprises introducing as an antifouling agent an alcohol having 1 to 20 carbon atoms, an alkyl or cycloalkyl ether having 2 to 20 carbon atoms, ammonia, an ester of an inorganic acid, a compound of a group IV element of the periodic table, alkyl and aryl amines, a sulfur-containing compound, or a mixture thereof at one or more locations in the recycle gas line in an amount sufficient to inhibit polymer buildup.