The cationic polymerization of cyclohexene oxide is initiated at room temperature upon irradiation at lambda(inc) > 350 nm of CH2Cl2 solutions containing N-ethoxy-2-methylpyridinium hexafluorophosphate (EMP+PF6-) and one of the following compounds: thioxanthone, anthracene, perylene or phenothiazine. Poly(cyclohexene oxide) of molar mass exceeding 10(5) is produced. In the absence of EMP+PF6-, which is transparent at lambda(inc) > 350 nm, these sensitizers are ineffective. Acetophenone and benzophenone do not act as sensitizers. An initiation mechanism involving electron transfer from the excited sensitizers to EMP+ ions is proposed. In flash photolysis experiments, electron transfer was evidenced by the formation of radical cations in the cases of anthracene, perylene or phenothiazine.