Since 1969, the Criminal Code of Canada has required that two breath alcohol tests be conducted “at least fifteen minutes apart” in order for the crown attorney to have the benefit of a 2-hour presumption. Other jurisdictions, however, allow for a shorter time interval between breath tests. This study used breath alcohol results from the City of Toronto for the period January 1 through December 31, 1995, and analyzed 2,759 duplicate Intoxilyzer 5000C test results with a statutory wait of “at least fifteen minutes” to see if the interval affected the differences between the duplicate results. The actual time between the tests ranged from 19 to 73 minutes (median = 22 minutes). Only BrAC’s (breath alcohol concentrations) greater than 0.020 g/210L were evaluated. Results were examined for normal distribution using the Kolmogorov-Smirnov (KS) test, skewness from the normal distribution was reported as required, and the Mann-Whitney U-test was used for the comparison of the medians of continuous variables. The analysis found that the distribution of the differences between the first and second breath tests ranged from 0 to 0.042g/210L and that this distribution was not normal. In addition, the data showed that the distributions were skewed to a lower second test result. This type of skewed distribution does not occur in jurisdictions where duplicate breath tests are conducted at a much shorter time interval of 3 to 5 minutes. The study concludes that a shorter time interval of 2 to 5 minutes would allow for a better agreement of duplicate breath samples, and a more efficient and rapid processing of arrested drinking drivers. References, 4 figures, and 1 table