The Comparative Survival Study (CSS) Oversight Committee prepared this report to address the recommendation provided by the Independent Scientific Advisory Board (ISAB) to prepare a retrospective synthesis of the methods and results to date on spring/summer Chinook and steelhead in the Columbia Basin. This ten-year summary report describes study methods, results and conclusions based on ten years of monitoring efforts. The Passive Integrated Transponder (PIT) data used in the CSS are analyzed retrospectively, incorporating all juvenile and adult recovery data available for the period 1996 through 2006. The Ten-Year Retrospective Summary Report analyzes the available PIT-tag data withinand across-years, assessing the effects of migration routes, environmental conditions and migration timing on juvenile reach survival rates and Smolt-to-Adult Return rates (SAR). These analyses provide for improved understanding of survival rates and the effects of various environmental conditions and management actions on those rates.