Until recently, the effects of wildfire on aquatic ecosystems in the southwestern USA have been given little attention. Wildfires in the early 90s and their impact on threatened and endangered fishes and their habitats increased concern for this management issue. In summer 2002, wildfires burned million of acres in the western USA. Several large (6000-40000 HA) wildfires occurred in the Southwest and provided opportunity to delineate the effects on a dozen native fishes -- several threatened and endangered species. Information was gathered on three different fires in New Mexico. In one stream, all fishes were lost in the fire-impacted reaches of stream. In the other two streams, a 70% reduction in total fish numbers was recorded. Based on data collected in summer 2002 from 1989 and 1990 fires, and a stream affected by a 1950 fire, immediate, post-fire stream water quantity and quality and both short and long-term alteration of habitat are primary determinants of effects on fishes. Species specific responses were recorded from one summer 2002 fires. Results indicate two listed species could be dramatically affected by post wildfire effects in southwestern stream ecosystems.