Residual Douglas-fir left after harvesting are dwarf mistletoe infected and pose a threat' to regeneration in some units. Removal of residuals, coupled with planned or completed site preparation and thinnings, will effectively reduce dwarf mistletoe incidence and increase future volume yields. The benefit/cost ratio based on timber values alone is <0.01/1 at 10 percent and 0.14/1 at 6 percent. Elimination of dwarf mistletoe infection for several rotations outweighs the economic benefits for the first rotation. Value added to the economy cannot be used in benefit/cost calculations, but will be a substantial sum. Control is recommended.