Both cis- and trans-stilbene react smoothly with fluoroxytrifluoromethane to afford, mainly by cis-addition, products of electrophilic fluorination. The reaction has been shown to proceed through discrete carbocations analogous to the intermediates well known from studies of conventional halogenation. The tendency toward cis-addition noted for electrophilic fluorination has been attributed to the involvement of tight ion pairs and, where appropriate, neighbouring group participation.