Specially designed allylic salts (addition-fragmentation agents, AFA) in conjunction with conventional radical initiators are shown to initiate cationic polymerization. The initiation mechanism involves addition of photochemically or thermally produced radicals to an AFA and subsequent fragmentation to yield reactive radical cations. For further extension of this new concept, self initiating AFAs were synthesized and used in photoinitiated cationic polymerization. For this purpose long absorbing chromophores ( Michler's ketone, benzophenone or morpholino ketone) which gives the possibility of producing radical sites upon irradiation were introduced in the structure of addition fragmentation agents. Thus, this type of initiators function without the requirement of additional free radical sources.