Brad Efron wrote this monograph shortly after the publication of his groundbreaking early papers on bootstrapping. It was the first and for many years the only major reference on bootstrapping. It is written in an intuitive style and provides the connection between the bootstrap and many of the other earlier resampling methods, especially the jackknife. Geometric arguments are often used to explain concepts. Today it is still a useful reference but is very much outdated as there have been many advances. There are now also several excellent reference books and texts on the bootstrap including the introductory text by Efron and Tibshirani published in 1993 and the text by Davison and Hinkley published in 1997. My book published by Wiley in 1999 is intended for practitioners and has over 1600 references.