Elevated ozone levels in urbanized areas of the United States are not only harmful to humans but pose a significant threat to urban landscapes.  In cities such as Baton Rouge, Louisiana, ozone levels commonly exceed attainment standards set by the EPA.  Even though ozone continues to rise in many urbanized areas, very little is known regarding turfgrass tolerance to ozone toxicity.  Two commonly grown warm-season turfgrasses, centipedegrass (Eremochloa ophiuroides) and St. Augustinegrass (Stenotaphrum secundatum) were exposed to acute ozone toxicity (200 ppb) using specially designed chambers.  Plants were exposed to ozone for 4 hours a day for a total of 8 hours over 2 days.  At the end of the second day, plants were visually rated for injury and photosynthetic fluorescence measurements were collected.  Centipedegrass showed no visual symptoms or changes in photosynthetic fluorescence.  Conversely, St. Augustinegrass exhibited mottling and necrosis on leaf tissue as well as reduced photosynthetic fluorescence.  Symptoms from St. Augustinegrass were similar to symptoms of St. Augustinegrass infected with the panicum mosaic virus.  Based on these findings, centipedegrass has greater tolerance of acute, high concentration ozone exposure compared to St. Augustinegrass.