An accessible text for the study of numerical methods for solving least squares problems remains an essential part of a scientific software foundation. Feedback that we have received from practicing engineers and scientists, as well as from educators and students in numerical analysis, indicates that this book has served this purpose. We were pleased when SIAM decided to republish the book in their Classics in Applied Mathematics series.

The main body of the book remains unchanged from the original book that was published by Prentice-Hall in 1974, with the exception of corrections to known errata. Appendix C has been edited to reflect changes in the associated software package and the software distribution method. A new Appendix D has been added, giving a brief survey of the many new developments in topics treated in the book during the period 1974–1995. Appendix D is organized into sections corresponding to the chapters of the main body of the book and includes a bibliography listing about 230 publications from 1974 to 1995.