EPDM containing dicyclopentadiene (DCPD) as diene monomer was hydroborated with 9-borabicyclo(3.3.1)nonane (9-BBN). The subsequent amination with monochloroamine was expected to result in EPDM with primary amine groups. The conversion of the residual unsaturation of DCPD of EPDM was complete, but the chemical structure of the amine-modified EPDM could not be fully elucidated. Hydrogenated DCPD (DCPDH), the low-molecular-weight analogue of DCPD incorporated in EPDM, was also hydroborated and aminated and the resulting product was isolated and extensively characterized. It was shown to consist of DCPDH coupled to 9-BBN via the B-atom with an NH unit inserted in one of the B-C bonds of the 9-BBN unit. The product is in fact a zwitterion RR'B-(OH)NH2+R ", which converts to the neutral RR'BNHR " upon dehydration. Using the analytical data of the low-molecular-weight product it was deduced that a similar structure is present in the amine-containing EPDM. Surprisingly, both amine-modified EPDM and DCPDH reacted as primary amines; for example, in the presence of anhydrides imides were formed. Finally, application of the amine-containing EPDM resulted in compatible blends of EPDM with poly(styrene-co-maleic anhydride).