Dwarf mistletoe is a serious problem on the Flathead Indian Reservation. Since the early 197o's, a procedure called thinning-sanitation has been applied to lightly infested stands. Evaluation of this procedure indicated that average dwarf mistletoe infection levels now range from 7 to 50 percent in larch and Douglas-fir treated 10 years ago. A second thinning, designed to remove the remaining infections, would leave an additional 30 percent of residuals infected. It is concluded that the thinning-sanitation procedure has not been effective in controlling dwarf mistletoe, even in what appear to be lightly infested stands.