The oxirane ring of epoxynaphthoquinones was reductively opened upon irradiation in the presence of triethylamine and, in addition, a cross adduct was obtained in the reaction with N,N-dimethylaniline in benzene. CIDNP signals observed in the reaction with N,N-dimethylaniline were interpreted as evidence for hydrogen atom abstraction in benzene and for electron transfer in acetone and acetonitrile