Sonoluminescence (SL) is generally attributed to the radiative recombination of hydroxyl radicals produced by the high temperatures and pressures associated with cavitation bubble collapse. SL from a single bubble has been observed in a levitation cell at 20 kHz, which supports this assumption. The pressure amplitudes ranged from 110 kPa for water to 170 kPa for 60% glycerin in water. Pulsation amplitudes were measured to be between five and ten times the equilibium radius. Such large amplitude steady-state pulsations have never been observed before. The possible mechanisms by which stability is maintained will be discussed and theoretical calculations of temperatures and pressures inside the bubble will be presented. [Work supported by ONR.]