UV spectra and kinetics for the reactions of alkyl and alkylperoxy radicals from methyl tert-butyl ether (MTBE) were studied in 1 atm of SF₆ by the pulse radiolysis-UV absorption technique. UV spectra for the radical mixtures were quantified from 215 to 340 nm. At 240 nm. σ_R = (2.6 ± 0.4) × 10^-18 cm² molecule^-1 and σ_RO2 = (4.1 ± 0.6) × 10^-18 cm² molecule^-1 (base e). The rate constant for the self-reaction of the alkyl radicals is (2.5 ± 1.1) × 10^-11 cm³ molecule^-1 s^-1. The rate constants for reaction of the alkyl radicals with molecular oxygen and the alkylperoxy radicals with NO and NO₂ are (9.1 ± 1.5) × 10^-13, (4.3 ± 1.6) × 10^-12 and (1.2 ± 0.3) × 10^-11 cm³ molecule^-1 s^-1, respectively. The rate constants given above refer to reaction at the tert-butyl side of the molecule.