We describe and test Forest 5, an individual-tree growth and dynamics model for the Great Lakes region. Forest 5 includes reasonably detailed descriptions of physiology, soil and climate, and incorporates both empirically- and physiologically-based modules from Crobas, Linkages, Forest, Sortie, PnET, 3-PG, and other sources. We have evaluated a nonspatial variant of Forest 5 as a scientific statement of knowledge by comparing simulation results to a battery of ecosystem-level expectations. We also evaluated the same model as a tool for management by comparing single-species, single-age simulations against mensurational and ecological expectations. We finally compared multiple-species multi-age simulations against six measurements of permanent sample plots, spanning approximately 30 years, from a database from the University of Minnesota Cloquet Forestry Center. Here we describe Forest 5 in detail, introduce, explain, and apply the diagnostics, and interpret their results in the light of the model structure and goals. The model was judged defensible under certain circumstances but exhibited shortcomings that are probably due to nutrient cycling and the simulation of tree shape, crown shape, and competition. These shortcomings are in turn instructive in considering refinements to Forest 5 and possibly other models.