Intermolecular transylidation between halonium ylides under thermal and catalytic (rhodium (II) acetate) conditions, which makes it possible to synthesize a hitherto unknown kind of aliphatic chloronium ylides as well as a variety of bromonium and iodonium ylides, was developed. The uncatatyzed thermal transylidations of bromonium to iodonium ylides probably involve generation of a reactive carbene :C(SO2CF3)(2), being electrophilic in nature. Compared to the bromonium and iodonium ylides, the chloronium ylide serves as a much better progenitor for generation of carbenes; (or carbenoids) and efficiently undergoes cyclopropanation of olefins such as cyclooctadiene under uncatatyzed thermal conditions. A greater leaving group ability of the lambda(3)-chloranyl and lambda(3)-bromanyl groups compared to that of the lambda(3)-iodanyl group seems to be responsible for the observed differences in reactivity between these halonium ylides.