Mountain pine beetle populations began increasing in Glacier National Park in 1970. Numbers of infested trees increased steadily from an average of 12 to 115 per hectare from 1972 to 1976. Total hectares of infestation have increased from 445 in 1972 to 40,419 ha in 1976. Predictive equations estimate a cumulative loss of nearly 3 million trees by 1977. Silvicultural practices to reduce the phloem thickness/ tree diameter distribution in stands are the best known management alternatives. But because of the National Park Service policy to permit mortality as part of natural succession, application of these alternatives is not recommended.