[en] Unit 6 and 7 at Tokyo Electric Power Company's Kashiwazaki-Kariwa Nuclear Power Station are the first advanced boiling water reactor plants in the world, of which Unit 6 started up commercial operation in November 1996 and Unite 7 followed it in July 1997. This report describes the objectives of the ABWR development project that was decided on the basis of our experience in plant operation, discusses major features of the plant design adopted to achieve such objectives and the design and verification methods used for design improvements under the project. (author)