We have observed strong VHF plasma waves with amplitudes in excess of 0.1 mV/m (Hz)1/2 associated with 50 mA electron beam injections in the ionosphere. These observations were made up to 44 MHz, which is approximately 20 times the ambient plasma frequency. Data from three swept-frequency receivers carried on two daughter payloads have been analyzed to determine the emission spectra of the electron beam for various energies and currents. These results were obtained from the rocket-borne experiment SCEX 3 (Several Compatible EXperiments using a rocket-borne accelerator), NASA flight 39.002 UE, launched February 1, 1990, from Poker Flat Research Range (65.1¿N, 147.5¿W). Such VHF emissions from electron beams are normally considered to be caused by a beam plasma discharge (BPD) (Llobet et al., 1985). The accelerator payload also carried photometers, which measured luminosity at wavelengths of 391.4 nm and 380.5 nm. Several times during electron gun activity the measured luminosity increased much faster than proportional to the beam current. This nonlinear increase is evidence that a discharge is occurring in the vicinity of the accelerator payload. The uniform distribution of the luminosity around the accelerator payload implies that the observed discharge extends significantly outside the beam cylinder. Because the photometers did not view the beam region directly, there is no direct evidence that a beam plasma discharge is occurring. Neutral density gauges carried on the accelerator payload and a daughter payload measured a neutral density enhanced by ~3 orders of magnitude over model density profiles. This excessive neutral density (presumably caused by outgassing) may account for the discharge. A possible mechanism for igniting the beam plasma discharge in space is also presented. ¿ American Geophysical Union 1992