HEI Research Report 192 describes a multicenter study by John Balmes at the University of California–San Francisco, Phil Bromberg at the University of North Carolina–Chapel Hill, and Mark Frampton at the University of Rochester, New York. The study was designed to test whether ozone has short-term cardiovascular effects at present-day ambient levels. It evaluated respiratory and cardiovascular outcomes in 87 healthy participants (60 years old on average) who were exposed to 0, 70, or 120 ppb ozone for 3 hours while exercising moderately.