A pulse radiolysis technique was used to measure the UV absorption spectra of (CH₃O)₂CHOCH₂(.) and (CH₃O)₂CHOCH₂O₂(.) radicals derived from trimethoxymethane over the range 220-320 nm, σ_{250 nm} (CH₃O)_2- CHOCH₂(.) = (2.8 ± 0.4) × 10^-18 and σ_250nm (CH₃O)₂CHOCH₂O₂(.) = (3.5 ± 0.4) × 10^-18 cm² molecule^-1. The self-reaction rate constants for (CH₃O)₂CHOCH₂(.) and (CH₃O)₂CHOCH₂O₂(.) radicals, defined as -d[(CH₃O)₂CHOCH₂(.)]/dt = 2k₅[(CH₃O)₂CHOCH₂(.)]² and -d[(CH₃O)₂CHOCH₂O₂(.)]/dt = 2k₆, _obS[(CH₃O)₂-CHOCH₂O ₂(.)]² were k₅ = (3.5 ± 0.5) × 10^-11 and k_{6 obs} = (1.3 ± 0.2) × 10^-11 cm³ molecule^-1 s^-1. Rate constants for reactions of (CH₃O)₂CHOCH₂O₂(.) radicals with NO and NO₂ were k₇ = (9.0 ± 1.2) × 10^-12 and k₈ = (1.0 ± 0.2) × 10^-11 cm³ molecule^-1 s^-1, respectively. Rate constants for the reaction of OH radicals and F atoms with trimethoxymethane and the reaction of (CH₃O)₂CHOCH₂(.) radicals with O₂ were k₁ = (6.0 ± 0.5) × 10^-12, k³ = (3.0 ± 0.7) × 10^-10, and k₂ = (9.2 ± 1.5) × 10^-12 cm³ molecule^-1 s^-1, respectively. Relative rate techniques were used to measure k(Cl + trimethoxymethane) = (1.5 ± 0.2) × 10^-1 cm³ molecule^-1 s^-1. OH-radical-initiated oxidation of trimethoxymethane in air gives dimethyl carbonate in a molar yield of 81 ± 10%. These results are discussed with respect to the atmospheric chemistry of automotive fuel additives.