The sublimation of Ar/H 2O, CO/H 2O, and CO 2/H 2O mixtures condensed at 23–30 K was investigated. The release of the more volatile component of the ice mixture occurred in several discrete temperature regions. Gas release, as monitored by a mass spectrometer, was correlated with changes in the infrared spectrum of the solid ice. The results are in substantial agreement with those of Bar-Nun and co-workers, who studied ice sublimation using mass spectrometry alone, and Sanford and Allamandola, who used infrared spectroscopy alone. Several different concentrations were used for all gas/H 2O mixtures, and relative peak intensities during warming were found to depend on the initial gas/H 2O ratio. The sublimation of H 2O, CO/H 2O, and CO 2/H 2O ices following irradiation by 1-MeV protons was also studied. Irradiation of CO or CO 2 containing ices resulted in CO 2 or CO release, respectively, in addition to the original species. Some implications for cometary phenomena are given.