The present study evaluated the effects of a single three hour ozone exposure on erythrocyte parameters of male Dawkin‐Hartley guinea pigs that were reared on diets high or low in vitamin C for 11 days prior to the ozone exposure. The results indicated that consumption of diets highly different in vitamin C levels did not have a significant effect on ozone induced alterations in erythrocyte parameters although there was a trend toward higher methemoglobin values in the ozone treated guinea pigs reared on the low vitamin C diets as compared to similarly exposed animals given the high vitamin C diet.