U.S. intelligence officials claimed Pakistan was a key supplier of uranium enrichment technology to North Korea, and some media reports suggested that Pakistan had exchanged centrifuge enrichment technology for North Korean help in developing longer range missiles. U.S. official statements leave little doubt that cooperation occurred, but there are significant details missing on the scope of cooperation and the role of Pakistan's government. The roots of cooperation are deep. North Korea and Pakistan have been engaged in conventional arms trade for over thirty years. Weapons of mass destruction (WMD) trade between North Korea and Pakistan raises significant issues for Congress, which are discussed at length in this report.