ISAJET 7.40: A Monte Carlo Event Generator for pp, bar pp, and e^+e^- Reactions

ISAJET is a Monte Carlo program which simulates $pp, \bar pp$ and $e^+e^-$ interactions at high energies. This document summarizes the physics underlying the program and describes how to use it. New features of Version 7.40 include generation of $W+H$ and $Z+H$ events, non-minimal GMSB models, and use of the experimental $\alpha_s(M_Z)$ by default.