Mountain pine beetle reached epidemic levels in second-growth ponderosa pine stands on Bureau of Indian Affairs and private lands on the Crow Indian Reservation. Approximately 9,106 trees containing 420,266 merchantable board feet were killed from 1971 to 1973. This is about 24 percent of the merchantable ponderosa pine in stands surveyed. Stands are stagnated, and trees appear stressed which is probably predisposing them to beetle attack. An increase in size of area infested and number of trees killed is expected in 1974. Commercial thinning to remove infested trees and reduce basal area is recommended to alleviate the problem. Slash disposal is highly recommended during logging to prevent buildup of pine engraver beetle populations.