The results from a collaborative test of the U.S. Environmental Protection Agency Test Method 8 are presented. In the collaborative test six laboratories simultaneously sampled the same stack at a sulfuric acid plant using two Method 8 sampling trains per laboratory. The collaborative test determined that the repeatability of the method was 7.61 mg sulfuric acid per cu m and 22.30 mg sulfur dioxide per cu m. Similarly, the reproducibility of the method was 8.43 mg sulfuric acid per cu m and 31.10 mg sulfur dioxide per cu m. The estimates of precision were determined to be independent of the pollutant concentration over the concentration range measured.