Fires have burned through Pacific Northwest forests for thousands of years, as evidenced by pollen and charcoal deposits from early forests, fire scars on trees, analysis of stand age classes, and early settler and explorer accounts. Fire is not a uniform process in time or space on the landscape. The frequency, intensity, and extent of fires differ considerably across the Pacific Northwest; these differences can be categorized by the concept of fire regime. In this chapter, past effects of high-, moderate-, and low-severity fire regimes in natural forests are described, with examples from several forest types in each regime. A comparison of historical and current fires in the Pacific Northwest reveals that modern fire control policies have been effective at reducing acreage burned by free-ranging wildfire. Ironically, success at fire suppression has allowed more uniform and larger fuel loads across the landscape, resulting in more severe fire effects. The objectives of fire management must be broader than simply fire suppression if land management objectives are to be met.