This chapter addresses ASME Code Section XI, Subsections IWE and IWL, for nuclear power plant containments. Subsection IWE provides requirements for preservice and inservice examination/inspection, repair/replacement (R/R) activities, and testing of Class MC (metal containment) pressure-retaining components and their integral attachments and R/R activities. It also provides requirements for testing of Class CC (concrete containment) pressure-retaining components and their integral attachments for boiling water reactors (BWRs) and pressurized water reactors (PWRs). Similarly, Subsection IWL provides requirements for preservice and inservice examination/inspection, R/R activities, and testing of the reinforced concrete and post-tensioning systems of Class CC components for BWRs and PWRs. Together with Subsection IWA, a comprehensive basis is provided for ensuring the continued structural and leak-tight integrity of containments in nuclear power plants. The chapter includes a brief history of the development of ASME Code requirements, the latest information on the U.S. Nuclear Regulatory Commission regulatory review and incorporation of recent ASME Code Editions and Addenda, and current listings of U.S. ‘construction-complete’ commercial nuclear power plants and their containment types and operating status. A summary of recent nuclear industry developments in advanced plant designs and a discussion of the as-yet-unrealized ‘U.S. nuclear renaissance’ are also presented, along with information on the global demand for energy and the current status of commercial nuclear power around the world. Lastly, the current Subsection IWE and IWL Commentaries, as approved and maintained by the ASME Working Group on Containment, are included.