We present the first observation of self-amplified spontaneous emission (SA
SE) in a free-electron laser (FEL) in the vacuum ultraviolet regime at 109
nm wavelength (11 eV). The observed free-electron laser gain (approximately
3000) and the radiation characteristics, such as dependency on bunch charg
e, angular distribution, spectral width, and intensity fluctuations, are al
l consistent with the present models for SASE FELs.