(Please note, this is an extended abstract only) Extensive tree mortality occurred in ponderosa pine forests and pinon-juniper woodlands of Arizona from 2001-2004. This mortality has been attributed to a combination of an extensive drought, overstocked stands of pine, and increased bark beetle populations. A complex of Ips and Dendroctonus species worked in concert to kill ponderosa pine. Pinon pine was attacked primarily by pinyon ips and to a lesser extent twig beetles. Initial tree mortality was associated with poor site quality (i.e., shallow soils, cinder hills, south-facing aspects, and lower elevations) and high tree densities.