Selective excitation of benzil in the presence of 3-hydroxyflavone (3HF) in fluid solution results in diffusional triplet energy transfer from benzil to 3HF, and the T n ←T 1 absorption spectrum of 3HF (acceptor) was determined by transient absorption spectroscopy. It is demonstrated that red probe pulse excitation of the lowest triplet state (T 1) of the normal tautomer yields green fluorescence from the phototautomer in the lowest excited singlet state (S′ 1). Generation of S′ 1 upon the excitation of T 1 may be ascribed to an efficient T n →T′ n proton transfer followed by T n ′→T′ 2 relaxation and T′ 2→S′ 1 reverse intersystem crossing.