Since adoption of the Northwest Forest Plan (NWFP) in the early 1990s, there has been a fundamental shift in forest management practices on federal lands in western Oregon and Washington. Commodity-driven clearcut regeneration harvests have given way to thinnings intended to enhance development of late-successional forest habitats and to conserve important aquatic and riparian ecosystems. Density Management in the 21st Century: West Side Story presents abstracts and peer reviewed papers from a regional conference highlighting more than twenty years of research related to forest thinning in the NWFP area. Presentations from the BLM Density Management and Riparian Buffer Study provide a focal point, with presentations from additional studies providing for a more complete overview of the west-side thinning science. The contributions are organized as five topical themes: The Regional and Landscape Context for Density Management in the Northwest Forest Plan Era; Implementation and Influences of Density Management in the Terrestrial Ecosystem; Riparian and Aquatic Ecosystems and their Responses to Thinning and Buffers; Socioeconomics and Operations; and Thinning and Adaptation. Collectively, the contributions summarize many important forest dynamics and ecosystem responses to partial overstory removals. Interactions between aquatic and riparian ecosystem conservation measures and upland harvest are emphasized. Targeting resource management practitioners, decision-makers and researchers, the collected works provide a reference to the current and future roles and issues of density management as a tool for forest ecosystem management.