The Grand Canyon Forests Partnership’s initial wildland/urban interface experimental treatments were started in 1998 in cooperation with the Coconino National Forest and Rocky Mountain Research Station. The experiments had multiple objectives, but our focus in this paper is only on the treatment effects on potential fire behavior. The greatest concern in the wildland/urban interface is crownfire, both “passive” crownfire (tree torching) and “active” crownfire (fire spreading through the canopy). Crownfires spread rapidly (Rothermel 1991), resist control by hand crews and often mechanical or aerial equipment (Pyne and others 1996), and threaten structures with intense heat and firebrand showers (Cohen 2000).