Oventodted70-1090-year-old stands ofpondemsspineanmedium-tolow-qu were thinned in 1980 to 40.55. and 70 perant of n o d basal srea and c a n p a d to an unthinned cmuol. Mortality, diameter, and height in thesenorthem W o m i a stands wore m c a s u d annually from 1980 to 1987. After 8 years. mortality, primarily fmm mountain pine beetle (D~ndroclonrrr pondcrmae) and annosus rmt direare (Hcrcrobaridion mnosun), was reduced 100.95, and 86 percent relative to incming amounts of reserve basal area. Thinned stands averaged five times more cubic-foot volume gmwth than unthinned stands. More gmwth andlesr monality cwld result fmm mating similar stands elsewhere.