  This article contains lecture notes on the constrained path Monte Carlo
method and its applications to study the Hubbard model. The lectures were given
at the NATO Advanced Summer Institute held in Ithaca NY (1998). The article is
published as a chapter in the book `Quantum Monte Carlo Methods in Physics and
Chemistry,' Ed. M.P. Nightingale and C.J. Umrigar (Kluwer Academic Publishers,
1999).
