The bromomethylperoxy radical, CH2BrOO, has been generated in cryogenic matrices. Six fundamental bands for CH2BrOO have been observed in an argon matrix at 5 K. The experimental frequencies (cm
1) are: m4 = 1274.3, m5 = 1229.4, m6 = 1086.7, m7 = 961.8, m8 = 879.9, and m10 = 515.4, two of which are detected for the first time. Ab initio calculations have been performed employing coupled-cluster methods. The experimental frequencies are shown to be in good agreement with the computation as well as the four bands (m4, m6, m7 and m8) observed by Huang and Lee in the gas phase.