Four hundred and four pairs of breath- and blood-alcohol results from specimens collected within 1 hour of each other were studied. Blood-alcohol concentrations ranged from zero to 0.421 percent weight per volume (w/v). Breath-alcohol concentrations ranged from zero to 0.44g/210L. The mean Breathalyzer result was 0.16g/L. The mean blood-alcohol result was 0.176 percent w/v. Compared to the blood-alcohol result, Breathalyzer results were lower by more than 0.10g/210L 61 percent of the time, within 0.01g/210L 33 percent of the time, and higher by more than 0.01g/210L 6 percent of the time. (Author abstract)