This Fire Regime Synthesis details characteristics of presettlement (i.e., before Euro-American settlement), historical (i.e., any past record), and contemporary (i.e., 1980s to present) fuels and fire regimes in ponderosa pine and montane mixed-conifer communities in the East Cascade Mountains in the northwestern United States. Stand structure and species composition varies within and among these communities due to variation in site characteristics, climate, disturbance history, and successional stage. Although historical landscapes were successionally diverse, they were characterized by a large proportion of low-density, open-canopy forest dominated by large, old, fire- and drought-tolerant trees (mostly ponderosa pine), with small areas of higher-density forest, and small openings without trees. These stand structures are compatible with a presettlement fire regime dominated by frequent, low- and mixed-severity fires, with high-severity fire effects mostly limited to relatively small (<100-200 ha) patches. This fire regime maintained low fuel biomass, dominated by flammable, often continuous surface fuels, with few ladder fuels, and relatively widely spaced crown fuels. Our analyses found presettlement mean fire interval (MFI) averaged 12 years with a maximum MFI of 24 years in the ponderosa pine forest zone, and MFI averaged 20 years with a maximum MFI of 100 years in the montane mixed-conifer forest zone. Historically, lightning-caused fires could ignite as early as May and as late as October, although fire-scar analyses across all forest types suggest a dominance of late growing season and dormant season fires, with some variability among studies. Lightning ignitions were most common, although American Indians also ignited fires, within and outside lightning season. Evidence suggests that most presettlement fires were small (<400 ha), and larger fires were infrequent. Large fires and widespread fire years were most frequent during relatively warm, dry summers at both site and regional scales. Wetter than average antecedent conditions may be related to large fires on the driest ponderosa pine sites.