The \“Input-Output Handbook\” describes the concepts and methods that underlie the preparation of the benchmark input-output (I-O) accounts of the United States. The handbook is intended to provide new employees with a grounding in the basics of I-O accounting, background on the development and uses of the accounts, and an introduction to the process of preparing the I-O estimates and tables. It is also intended to provide existing employees with information that will broaden their understanding of particular aspects of the work. The handbook does not provide detailed descriptions of methodology or of database operations. The descriptions of methodology that are presented in the handbook are primarily based on the 1997 benchmark accounts, though some updates and indications of future changes are included. Thus, the handbook is intended to be a living reference, whereby additional or updated information can be added as available and appropriate.