Congress has long been concerned about whether U.S. policy advances the national interest in reducing the role of the People's Republic of China (PRC) in the proliferation of weapons of mass destruction (WMD) and missiles that could deliver them. Recipients of China's technology reportedly included Pakistan, North Korea, and Iran. This CRS Report, updated as warranted, discusses the security problem of China's role in weapons proliferation and issues related to the U.S. policy response since the mid-1990s. China has taken some steps to mollify U.S. and other foreign concerns about its role in weapons proliferation. Nonetheless, supplies from China have aggravated trends that result in ambiguous technical aid, more indigenous capabilities, longerrange missiles, and secondary (retransferred) proliferation. Unclassified intelligence reports told Congress that China was a "key supplier" of technology, particularly with PRC entities providing nuclear and missile-related technology to Pakistan and missile-related technology to Iran.