Abstract Recent interpretations of Evans' experiments on the oxygen-induced singlet-triplet transitions in aromatic molecules are briefly discussed. In addition to the oxygen-induced singlet-triplet absorption for naphthalene there is a second absorption band which is possibly due to a simultaneous transition, i.e. a transition of the aromatic molecule from the ground state to the lowest triplet excited state and the 3Σ − → 1Δ transition of the oxygen molecule. Singlet-triplet transitions can also be stimulated by solvents containing heavy atoms. The results are shown for naphthalene, pyrene and fluoranthene with the solvents ethyl iodide, bromoform and iodobenzene. A qualitative discussion is given.