[en] EXFOR is the agreed exchange format for the transmission of nuclear reaction data between national and international nuclear data centers for the benefit of nuclear data users in all countries. The IAEA Nuclear Data Section uses the EXFOR system not only for the center-to-center data exchange but also as its data storage and retrieval system. This NDS EXFOR MANUAL therefore contains the agreed EXFOR coding rules and format, supplemented by NDS internal compilation rules. The EXFOR system and the EXFOR nuclear data library with several million data records originate from the cooperation of an increasing number of data centers whose names and addresses can be found inside the Manual. Their contributions and cooperative efforts are gratefully acknowledged. (author)