[from the text] Little is known about the effect of fire injury on pines infected with dwarf mistletoe (Arceuthobium ssp.) (Alexander and Hawksworth 1975). A prescribed burn on permanent plots in ponderosa pine (Pinus ponderosa subsp. scopulorum [Engelm.] E. Murray) on the South Rim of Grand Canyon National Park, Arizona, enabled us to compare fire-kill in trees with various intensities of dwarf mistletoe infection (Arceuthobium vaginatum subsp. cryptopodum [Engelm.] Hawksw. and Wiens). Although fire has long been considered the primary natural control agent of dwarf mistletoe (Hawksworth 1961, Roth 1953), little quantitative information on the subject is available, particularly for ponderosa pine. Koonce and Roth (1980, 1985) studied the effects of prescribed fire on survival of ponderosa pines affected by a similar dwarf mistletoe (Arceuthobium campylopodum Engelm.) in Oregon. They concluded that the dwarf mistletoe could be partially sanitized from thinned and unthinned ponderosa pine stands by prescribed understory burning. Their studies were conducted in immature, even-aged stands and not in uneven-aged stands such as we describe here for the Grand Canyon study. The objective of this study was to determine the effect of various combinations of crown scorch and dwarf mistletoe infection on first-year mortality of ponderosa pine.