We have assembled regional networks of crossdated fire-scar chronologies from forest stands in the Southwest (Arizona, New Mexico) and the Sierra Nevada of California. These chronologies extend back at least to AD 1700. Other fire historians have compiled networks of fire-scar chronologies from the east side of the Cascade Range in Washington and Oregon, the Rocky Mountains of Colorado, and the northern Great Plains. An outstanding feature of within-region comparisons of fire-scar chronologies is the high synchroneity of certain fire years. There is also high synchroneity of years when few fires were recorded within regions. Since most of the sampled stands are too distant for fire spread between them, this synchroneity is almost certainly due to regional climatic factors. Comparisons of synchronous large and small fire years between regional fire-scar networks from the Southwest, Sierra Nevada, and the Pacific Northwest reveal interesting spatial patterns that correspond with broad-scale climatic patterns, such as ENSO-teleconnected precipitation and drought. A common pattern, for example, is an inverse relation between the Southwest and Pacific Northwest in fire activity and in winter rainfall during extreme ENSO events. Other patterns show synchronous fire activity in the Southwest and Sierra Nevada during some drought events, and asynchronous during others. These findings have a number of important implications for our understanding of the spatial response of regional fire regimes to climatic variability, and the potential of using this understanding for allocating fire fighting or prescribed burning resources at continental scales.