This report summarizes six studies that compare site index relations between 24 hardwood and conifer species in the Upper Great Lakes area of the United States and Canada. These six studies have many regression models and graphs for comparing site index between forest species thus providing tools for estimating site index for alternative tree species based on direct site index measurements using tree species actually present in forest stands. Thus the objective of this summary paper is to summarize these models so that we can provide the most accurate tools available for estimating the tree species that are most productive and economically valuable for management on each forest site.