This is GAO's eighth annual assessment of selected Department of Defense (DOD) weapon programs. The report examines how well DOD is planning and executing its weapon acquisition programs, an area that has been on GAO's high-risk list since 1990. This year's report is in response to the mandate in the joint explanatory statement to the DOD Appropriations Act, 2009. The report includes (1) observations on DOD's efforts to manage its portfolio of major defense acquisition programs; (2) an assessment of the knowledge attained by key junctures in the acquisition process for a subset of 42 weapon programs from the 2009 portfolio; (3) data on other factors that can affect program execution; and (4) examples of how DOD is implementing recent acquisition reforms. To conduct the assessment, GAO analyzed data on the composition of DOD's portfolio of major defense acquisition programs. GAO did not analyze the cost and schedule performance of the portfolio because DOD did not issue timely or complete Selected Acquisition Reports for the second consecutive presidential transition. GAO expects to resume its portfolio analysis in next year's assessment. GAO also collected data from program offices on technology, design, and manufacturing knowledge, as well as on other factors that can affect program execution. GAO analyzed this data and compiled one- or two-page assessments of 70 weapon programs.