A comparison is made of the observed properties of electroglow on Jupiter, Saturn, and Uranus. It is found that the subsolar electroglow intensity measured by the Voyager Ultraviolet Spectrometer in the spectral region below 1110 ¿ scales as the inverse square of heliocentric distance to within 10%. There are large differences between the spectra from Uranus and the Jovian and Saturnian spectra at longer wavelengths, but this is a consequence of the different scattering properties of the Uranian atmosphere and is not related to electroglow. Excellent fits are obtained between model calculations of the spectrum of Rayleigh-Raman scattered sunlight and the observed spectra from Uranus. Our interpretation differs from previous analyses where the differences between the Uranian and Saturnian spectra were interpreted to be a consequence of different electron temperatures. It is also found that the local time variations of electroglow on all three planes are consistent with an excitation rate proportional to the solar flux. These correlations with solar flux suggest that electroglow is a direct consequence of the absorption of solar radiation in the upper atmosphere of the outer planets. The most promising production mechanism for electroglow appears to be fluorescence of solar radiation in the H2 Lyman and Werner bands. We calculate that fluorescence of solar ultraviolet radiation in the Lyman and Werner band systems of H2 may be responsible for a large fraction of the observed intensity on Jupiter, Saturn, and Uranus; however, it is not clear why this source should scale as the inverse square of heliocentric distance. We also suggest that chemical reactions related to H- photolysis may be important in the upper atmospheres of the outer planets. Both fluorescence and H- photolysis merit further investigation. ¿ American Geophysical Union 1987