New experimental measurements of the temperature dependence of theR′fluorescence of ruby (77°–450°K) have disclosed features not previously observed. Direct phonon transitions to nearby levels contribute less and indirect Raman processes contribute more to theR3′ linewidth than had previously been reported. Direct phonon relaxation from theR1′ andR2′ levels to the2Elevel contributes appreciably to linewidth of their fluorescence to the ground state.