This article summarizes mechanisms considered to explain electronic transport in organic and polymer devices, primarily light-emitting diodes. Four tables summarize models on the basis of thermal processes such as thermionic and field emission, a variety of tunneling paths, hopping, space-charge-limited models, and several field-dependent mobility models. Energy-band diagrams illustrate and compare selected models. This article catalogs the mechanisms in an effort to easily direct readers to the relevant literature for more detailed treatments. (C) 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2622-2629, 2003