This report presents a detailed comparison of air emission data generated at Canadian pulp and paper mill facilities during the recent Forest Products Association of Canada's 20-mill study with similar data generated in the U.S. over the past decade or so. Included in the comparison are emissions for certain key speciated volatile organic compounds (including methanol, acetaldehyde, methyl ethyl ketone, and formaldehyde) from a range of pulp and paper mill sources. These sources include vacuum drum type brownstock washers, kraft bleach plants, oxygen delignification systems, direct contact evaporator (DCE) and non-direct contact evaporator (NDCE) kraft recovery furnaces, smelt dissolving tanks, lime kilns, thermomechanical pulping (TMP) and groundwood pulping operations, and paper machines processing mainly mechanical pulp. The individual mill source emissions and their medians for the Canadian mills were compared with median emissions for the corresponding U.S. mill sources and also with the median and range for the combined Canadian-U.S. data sets. Outliers arising from application of statistical treatment procedures to the combined data sets were identified. Besides VOCs, the comparison included criteria air pollutants such as total pariculate matter (TPM), PM 10, PM 2.5, CO, SO 2 and NO X for DCE and NDCE furnaces; total reduced sulphur (TRS) for NDCE furnaces; TPM and TRS for smelt dissolving tanks; TPM, PM 10, PM 2.5, SO 2 and TRS for lime kilns; SO 2, NO X, CO and TRS for thermal oxidizers; TPM, SO 2 and NO X for sulphite recovery furnaces; and trace metals for DCE/NDCE recovery furnaces, smelt dissolving tanks and lime kilns. The comparison for select VOCs showed that most of the data in the two groups were comparable in that the medians were similar and much of the Canadian data fell within the range for the U.S. data. As such, combining the two data sets into one robust data set makes much sense. Criteria air contaminant emissions from Canadian and U.S. unit operations were also comparable. Trace metal emissions appeared to be similar for comparable unit operations within the two countries. However, limited evidence pointed to somewhat higher emissions of phosphorus and manganese from Canadian unit operations. In some cases, the extent of data available either in the U.S. or Canadian data sets was small; thus, a proper comparison could not be made. © 2005 by the National Council for Air and Stream Improvement, Inc.