Following a wildfire in 1994, the Tally Lake Ranger District in Northwestern Montana experienced a population explosion of Senecio jacobaea or tansy ragwort. This was only the second, and by far the largest infestation of this invasive weed in the state of Montana. Information derived from the Invaders Database was used to project the potential regional spread of tansy ragwort without management action. Historical records dating back to 1901 were used to project the likely future expansion of tansy ragwort within the five northwestern states. At a more local scale, with information from the Invaders Database and other sources, Dr. Rice was able to provide the Project Interdisciplinary Team with a tansy ragwort risk rating for disturbed and forested site conditions...The habitat type risk ratings, based on the Invaders Database, are being used to help set priorities for 1998 inventory efforts.