Fire regimes can be defined through the attributes of frequency, seasonality, size/extent, complexity, intensity, and severity. An understanding of fire regimes is imperative in understanding fire effects in different vegetation communities. In particular, an understanding of fire severity patch dynamics at a landscape scale is needed for an understanding of fire effects, current fire regimes and to help with fire monitoring. Landsat satellite imagery can be used to assess fire severity patterns at a landscape scale. This technology is being used to quantitatively define fire regimes for several vegetation types in the Sierra Nevada mountain range in California. This is being done as part of the Sierra Nevada Frameworks Fire and Fuels Monitoring program. This program is using and testing both the Normalized Burn Ratio and the Kauth-Thomas transformation for mapping fire severity one-year post fire. The results are being compiled over time for different Sierra Nevada vegetation types to define fire regimes. This talk will be a summary of this program and the current results of both processing methods and our ability to define fire regimes.