We report on the field emission properties of single-wall carbon nanotube films, with emphasis on current-versus-voltage (I-V) characteristics and current stability, The films are excellent field emitters, yielding current densities higher than 10 mA cm(-2) with operating voltages that are far lower than for other film emitters, but show a significant degradation of their performances with time. The observed deviations from the Fowler-Nordheim behavior in the I-V characteristics point to the presence of a nonmetallic density of states at the tip of the nanotubes. (C) 1998 American Institute of Physics.