This report analyzes contract obligations for products, services, and research and development (R&D) by the U.S. Department of Defense (DoD), overall and by its key components (Air Force, Navy, Army and civilian agencies). It thereby seeks to provide an in-depth assessment of the trends currently driving more than half of all federal contract dollars. The report also includes findings on the industrial base supporting DoD in its missions. The timeframe analyzed extends from 1990 to 2011, and the Federal Procurement Data System (FPDS) is the primary source of data on government contract obligations in this report. In a change from previous reports, FPDS data for DoD are now available from 2000 to 2004, which makes the CSIS research team no longer dependent on Department of Defense Form 350 (DD350) data. Numbers will differ from previous reports due to a change in constant dollars (all dollar figures in this report are in Fiscal Year 2011 dollars and all years are fiscal years) and to continual updates of back-year data in FPDS. However, this difference is never greater than $10 billion between years.