In the last 5 years, the Department of Defense (DOD) has doubled its planned investments in new weapon systems from about $700 billion in 2001 to nearly $1.4 trillion in 2006. While the weapons that DOD develops have no rival in superiority, weapon systems acquisition remains a long-standing high risk area. GAO's reviews over the past 30 years have found consistent problems with weapon acquisitions such as cost increases, schedule delays, and performance shortfalls. In addition, DOD faces several budgetary challenges that underscore the need to deliver its new weapon programs within estimated costs and to obtain the most from these investments. This report provides congressional and DOD decision makers with an independent, knowledge-based assessment of selected defense programs that identifies potential risks and needed actions when a program's projected attainment of knowledge diverges from the best practices. Programs for the assessments were selected based on several factors including, (1) high dollar value, (2) stage in acquisition, and (3) congressional interest. The majority of the 52 programs covered in this report are considered major defense acquisition programs by DOD. This report also highlights higher level issues raised by the cumulative experiences of individual programs. GAO updates this report annually under the Comptroller General's authority.