The mountain pine beetle reached epidemic levels in second-growth 80-yearold ponderosa pine stands on the Ninemile Ranger District in 1969. The outbreak increased through 1971 and spread over 30,000 acres. Heavy infestation occurred on about 2,600 acres within this area. A two-stage survey was used during 1972 and 1973 to stratify the infestation, and obtain tree and volume loss estimates. This survey shows that about 109,284 trees were killed with an estimated volume loss of 613,743 board feet from 1970 to 1973. The outbreak has been declining since 1971. Surveys this year point toward a continued decline. However, some "hot spot" infestations will persist in pure,overstocked,second-growth stands. Commercial thinning is encouraged to release the stand, promote tree growth, and change the microenvironment, making it unattractive to mountain pine beetle.