The kinetics of the reactions of O 3 with 3-bromopropene and 3-iodopropene has been studied over the temperature range of 288–328 K at atmospheric pressure. The results obtained for the room temperature rate constants are (1.88 ± 0.22) × 10 −18 and (3.52 ± 0.43) × 10 −18 cm 3 molecule −1 s −1 , and the proposed Arrhenius expressions are k = (3.47 ± 1.28) × 10 −15 exp[(−2233 ± 110)/T] and k = (8.17 ± 2.12) × 10 −14 exp[(−2991 ± 80)/T] cm 3 molecule −1 s −1 for 3-bromopropene and 3-iodopropene, respectively. The atmospheric chemical lifetimes of these two compounds with O 3 were also estimated from these values.