Electrophilic and free radical additions to 5-ethylidenebicyclo [2.2. 1] hept-2-ene and 5- vinylbicyclo-[2.2. 1] hept-2-ene have been carried out with peracetic acid, hydrogen chloride, and methanol. In contrast to chlorosulfonyl isocyanate, peracetic acid primarily attacks the exocyclic double bond in 5-ethylidenebicyclo [2.2. 1] hept-2-ene. Several other electrophilic additions are discussed which demonstrate the unpredictable reactivity of the norbornyl ...