study area : longlac area (northwestern ontario)an individual tree mortality model was developed for understory ingrowth mixed species stands of boreal central ontario. data for the model came from long-term permanent sample plots initiated by the americancan and kimberly clark corporations and now maintained by the ontario ministry of natural resources. the model took the form of a logistic regression equation. tree size, stand density and basal area were found to be variables of particular importance, perhaps because they most directly reflect the situation of the tree within its particular system. also significant was average stand dbh and ingrowth density. the model correctly predicted 45% of the observed mortality and 70% of the observed survival in the data set used to develop the model. for the independent data set the model was able to correctly classify 30% of the observed mortality and 66% of the observed survival. future research efforts into mortality should include data collection on the causes of mortality and the interaction of a particular tree with its environment.