In a mixture of N-ethylcarbazole (ECZ) and 1,3-dicyanobenzene (DCB) in polymer films, electric field effects on fluorescence emitted from the locally excited (LE) state of ECZ and on exciplex fluorescence are affected by magnetic fields. Both nuclear hyperfine coupling between the singlet and triplet radical-ion pair states and reverse process from the singlet radical-ion pair state to the LE or exciplex fluorescent state play an important role in the synergy effects of electric and magnetic fields on fluorescence. The results for a mixture of ECZ and DCB are very different from those for a mixture of ECZ and dimethylterephthalate. (C) 2009 Published by Elsevier B. V.