"This report details the background to the establishment of the Canadian Intersite Decomposition Experiment (CIDET). The objectives of the study were: (a) to investigate the long-term rates of litter decomposition and nutrient mineralization over a broad range of forested ecoclimatic regions in Canada; (b) to study the relationship between decomposition rates, substrate quality and climate; (c) to assess the relative importance of site factors and microclimate on decomposition rates; (d) to assess the influence of site moisture regimes on decomposition rates; and (e) to test specific hypotheses on the observed pattern of litter decomposition.‍?‍?The study was established in 1992 and involved the preparation of almost 11 000 litter bags containing samples of sets of 12 standard litter types. Ten sets were placed in each of four replicate plots on 21 sites (18 upland and 3 wetland) representing a range of forested ecoclimatic regions. Each year for ten years, one set of bags is removed per plot and analyzed for mass loss and carbon, nitrogen and phosphorous content.‍?‍?The 21 sites cover a broad range of conditions from the wet (yearly precipitation 1782 mm), mild (9.3oC mean annual temperature) Douglas-fir and western hemlock forested sites in the pacific cordilleran ecoclimatic region, to the dry (261 mm), cold (-9.8oC), black spruce forested sites in the subarctic. Surface soil chemical properties generally reflected soil type, with brunisols and regosols having the lower %C and %N and higher pH's than podzols. In general sites in the pacific cordilleran or cool temperate were warmer, wetter and had forests with higher basal area, mean DBH, and height that those in the other ecoclimatic regions. Sites in the boreal, subarctic and transitional grassland formed a board group that could be distinguished from the cordilleran which were at a higher elevation and had forests with generally lower stand densities.‍?‍?CIDET is a cooperative study involving 20 researchers from the Canadian Forest Service, universities and provincial ministries The successful establishment of CIDET complements similar studies underway in the U.S. and Europe. Together these studies will increase our understanding of the relationship between climate, litter quality, and decomposition processes."