Exposure of male Sprague‐Dawley rats to 0.3 ppm ozone for 3 hours resulted in a time‐delayed increase in serum and hepatic reduced ascorbic acid levels as compared to controls (0.0 ppm O3) which exhibited an immediate increase in hepatic and serum ascorbic levels. After 24 hours ascorbic acid levels in both groups approached but did not return to pre‐exposure values. The immediate increase in ascorbic acid levels in the controls was unexpected and may reflect previously unrecognized chamber and/or handling effects.