Two Nicotiana tabacum L. cultivars, ‘North Carolina 88’ and ‘Coker 319′, were grown in a charcoal-filtered greenhouse and treated with three different herbicides according to the herbicide labels. Labeled rates (X) for diphenamid (N,N-dimethyl-2,2-diphenylacetamide), isopropalin (2,6-dinitro-N,N-dipropylcumidine), and pebulate (S-propyl butylethylthiocarbamate) were 9.2 kg/ha, 2.3 kg/ha, and 6.2 kg/ha, respectively. Three weeks after treatment with 1/2X, X, or 2X rates of herbicide, half of the plants were fumigated with 15 μl/liter ozone for 2.5 h for four consecutive days. North Carolina 88 and Coker 319 grew equally well and were equally sensitive to ozone injury. Ozone reduced plant height and levels of reducing sugars and total nonstructural carbohydrates of both cultivars. Isopropalin, at X and 2X, reduced the ozone sensitivity and growth of both cultivars, while the X rate of pebulate reduced the ozone sensitivity of North Carolina 88. The chemical composition of the plants was not correlated with the sensitivity of the tobacco plants to ozone-induced injury. The major factors governing fleck intensity, growth, and chemical compositions were ozone and herbicide treatments.