We assessed tree mortality and volume loss resulting from recent or current jack pine budworm defoliation in jack pine (Pinus banksiana) stands in the northern Lower Peninsula (NLP) and in the Raco Plains area of the Hiawatha National Forest (Raco) and Ottawa National Forest (ONF) in the Upper Peninsula of Michigan. Budworm defoliation ranged from negligible to relatively high in some stands. Annual radial growth, top-kill and mortality resulting from budworm defoliation or other causes were quantified in plots in a total of 152 stands. Tree mortality was highest in ONF, averaging 30%, compared to 16% in Raco, and 14% in the NLP. The percentage of top-killed jack pine trees averaged 3.0, 8.0, and 1.5% in the NLP, Raco, and ONF, respectively. Relationships between site and stand inventory variables and tree growth and mortality were examined. High quality sites with site index values of 56 ft. or better had higher percentage mortality than stands on poorer sites in Raco and ONF. Mortality was lowest in understocked stands with basal area less than 70 ft²/acre in all three regions. Top-kill was notably high in Raco on high quality sites with a site index value greater than 56 ft. and basal area of 70-110 ft²/ acre. Top-kill was highest on younger sites with low site index values in the NLP. Percentage mortality was highest among suppressed trees in all three regions, averaging 50.7%. Percentage top-kill was greater among intermediate class trees in all regions, averaging 8.0%. Additional plots will be established and surveyed in 2002.