The reaction of bicyclo[2.1.1 ]heptene (norbornene) with N-bromosuccinimide (NBS) in moist dimethyl sulfoxide (DMSO) has been examined in detail. The structures of the products have been elucidated and it has been shown (contrary to an earlier report) that no 2,3-bromohydrin products are obtained. In addition, bromohydrins which were not obtained, but which might have been, a priori, expected, were synthesized and shown to be stable to the reaction conditions. The products which were obtained, also stable to the reaction conditions, are accounted for on the basis of ionic and free-radical processes.