The atmospheric chemistry of methyl ethyl ether, CH3CH2OCH3, was examined using FT-IR/relative-rate methods. Hydroxyl radical and chlorine atom rate coefficients of k(CH3CH2OCH3+OH) = (7.53 ± 2.86) × 10−12 cm3 molecule−1 s−1 and k(CH3CH2OCH3+Cl) = (2.35 ± 0.43) × 10−10 cm3 molecule−1 s−1 were determined (297 ± 2 K). The Cl rate coefficient determined here is 30% lower than the previous literature value. The atmospheric lifetime for CH3CH2OCH3 is approximately 2 days. The chlorine atom–initiated oxidation of CH3CH2OCH3 gives CH3C(O)H (9 ± 2%), CH3CH2OC(O)H (29 ± 7%), CH3OC(O)H (19 ± 7%), and CH3C(O)OCH3 (17 ± 7%). The IR absorption cross section for CH3CH2OCH3 is (7.97 ± 0.40) × 10−17 cm molecule−1 (1000–3100 cm−1). CH3CH2OCH3 has a negligible impact on the radiative forcing of climate