The light output and the current driving tris-(8-hydroxyquinolinato) aluminum (III) (Alq(3))-based light-emitting-diodes were found to increase by up to 5% and 3%, respectively, as an external magnetic field increased to 300 mT. The positive magnetic-field effects were sensitive to the applied voltage. These observations made clear that the emissive singlet exciton formation proceeds via a correlated electron-hole pair state and the excitonic injection of electrons contributes to the driving current, the concentration of singlet excitons being modulated by the hyperfine scale magnetic-field-dependent mixing of singlet and triplet pair states constituting precursors of molecular excitons. (C) 2003 Elsevier B.V. All rights reserved.