Ozone is the major air pollutant damaging crops and other vegetation. It causes oxidative stress, resulting in increased synthesis of secondary metabolites. Anthocyanins are naturally occurring secondary metabolites that increase in concentration to fight free radicals and lower damage in leaves. Arabidopsis thaliana, a small flowering plant with short lifecycle is an ideal model organism. Three seed lines varying in anthocyanin production (TT-3, Blh-1, Pap-1) were compared to wild type Col-1. Three other lines were selected with mutations in other antioxidant defenses (Vtc-1, GPA-1, Des-1). Three- to four-week-old seedlings were exposed to 0ppb, 150ppb, 300ppb, 450ppb ozone for eight hours on three consecutive days. Anthocyanin concentrations were determined before exposure and one week after exposure. Lines with more anthocyanins were found to be more resistant as evidenced by less leaf damage. One week after exposures, the anthocyanin lines had increased anthocyanin concentrations up to 5X at 300ppb compared to 0ppb, but not as much at 450ppb. Pap-1, a transformed line that over produces anthocyanins, had the highest anthocyanin production. TT-3, a mutant with no anthocyanins, was severely damaged under 450ppb. In the lines with mutations in other antioxidant defenses, Des-1 and GPA-1 were less sensitive to ozone due to enhanced antioxidant defenses and did not increase anthocyanin concentrations much when exposed to ozone. Vtc-1, deficient in the primary antioxidant defense ascorbate, increased its anthocyanin concentrations 8X even at 150ppb, perhaps in compensation for its lack of primary defense. Results suggest that genetic engineering to enhance anthocyanins could increase crop resistance.