Rate constants were measured for the gas phase reactions of ppm concentrations of ozone in air with acetylene, acetaldehyde and toluene as 8.6 ± 0.9, 3.4 ± 0.5 and 1.2 ± 0.6 × 10-20 cm3 molecule-1 sec.-1, respectively, using the O3/NO chemiluminesence detector. Toluene, xylene, methane and carbon monoxide were also investigated and upper limits for the rate constants were obtained. Combination with data on olefins and oxides of nitrogen gives a quantitative assessment of the various contributions to the removal of atmospheric ozone.