A pulse radiolysis technique was used to measure the UV absorption spectra of (CH3O)(2)CHOCH2(.) and (CH3O)(2)CHOCH2O2(.) radicals derived from trimethoxymethane over the range 220-320 nm, sigma(250) nm (CH3O)(2)CHOCH2(.) = (2.8 +/- 0.4) x 10(-18) and sigma(250) nm (CH3O)(2)CHOCH2O2(.) = (3.5 +/- 0.4) x 10(-18) cm(2) molecule(-1). The self-reaction rate constants for (CH3O)(2)CHOCH2(.) and (CH3O)(2)CHOCH2O(.) radicals, defined as -d[(CH3O)(2)CHOCH2(.)]/dt = 2k(5)[(CH2O)(2)CHOCH2(.)](2) and -d[(CH3O)(2)CHOCH2O2(.)]/dt = 2k(6) (obs)[(CH3O)(2)-CHOCH2O2(.)](2) were k(5) = (3.5 +/- 0.5) x 10(-11) and k(6) (obs) = (1.3 +/- 0.2) x 10(-11) cm(3) molecule(-1) s(-1). Rate constants for reactions of (CH3O)(2)CHOCH2O2(.) radicals with NO and NO2 were k(7) = (9.0 +/- 1.2) x 10(-12) and k(8) (1.0 +/- 0.2) x 10(-11) cm(3) molecule(-1) s(-1), respectively. Rate constants for the reaction of OH radicals and F atoms with trimethoxymethane and the reaction of (CH3O)(2)CHOCH2(.) radicals with O-2 were k(1) = (6.0 +/- 0.5) x 10(-12), k(3) = (3.0 +/- 0.7) x 10(-10), and k(2) = (9.2 +/- 1.5) x 10(-12) cm3 molecule(-1) s(-1), respectively. Relative rate techniques were used to measure k(Cl + trimethoxymethane) = (1.5 +/- 0.2) x 10(-10) cm(3) 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.