The rate constants for 5-hexen-2-one (allylacetone, C5H8O) reactions with OH and NO3 radicals and O-3 at (298 +/- 1) K have been measured. The constants are k(5-hexen-2-one,OH) = (4.49 +/- 1.02) x 10(-11) cm(3) molecule(-1) s(-1), k(5-hexen-2-one, NO3) = (2.16 + 0.21) x 10(-14) cm(3) molecule(-1) s(-1) and k(5-hexen-2-one, O3) = (9.17 + 0.15) x 10(-18) cm(3) molecule(-1) s(-1). The obtained rate constants are compared with those of similar ketones and alkenes. Mechanism for OH + 5-hexen-2-one reaction is proposed. In addition, the atmospheric life-times of 5-hexen-2-one with respect to OH and NO3 radicals and O-3 are calculated and discussed. (C) 2010 Elsevier B.V. All rights reserved.