Mountain pine beetle populations developed to epidemic level in 1970 on the Hebgen Lake Ranger District. Infested acreage increased from 78,000 in 1977 to 79,061 in 1978. More than 4 million trees (238 MMBF) were killed in 1978. Cold temperatures during December 1978 may cause a significant decline in the beetle population, resulting in a decline in the number of newly attacked trees in 1979. Potential mortality from the beetle can be reduced and prevented through an accelerated program of (1) logging infested trees, and (2) silvicultural treatment of green and infested stands to reduce the inventory of large diameter highly preferred trees. High valued lodgepole pine in recreation and administrative sites should be sprayed with the preventative chemical, Sevimo1-4, to protect trees from beetle attack until the epidemic declines.