The addition of IC1 and IBr to 1-methyl-4-t-butylcyclohexene has been investigated in chloroform and carbon tetrachloride and the distribution of the produced trans-iodohalogenides has been determined by NMR spectroscopy. The stereoselectivity of the addition was found to be determined by both the reversible electrophilic first step and the nucleophilic second step. The higher stereoselectivity of