Field emission electroluminescence (FEEL), observed during field emission from polycrystalline diamond films for the first time, is initiated at field emission currents above 1 muA. The electroluminescence spectra exhibit the main luminescence peak at 482 nm. Typically, the luminescence intensity increases with the emission current. Although the FEEL observed in diamond and carbon nanotube films is poorly understood, it seems to be related to certain types of defects in the films. (C) 2003 American Vacuum Society.