SUSYGEN is a Monte Carlo program designed for computing distributions and generating events for MSSM sparticle production in e +e − collisions. The Supersymmetric (SUSY) mass spectrum may either be supplied by the user, or can alternatively be calculated in two different models of SUSY breaking: gravity mediated supersymmetry breaking (SUGRA), and gauge mediated supersymmetry breaking (GMSB). The program incorporates the most important production processes and decay modes, including the full set of R-parity violating decays, and the decays to the gravitino in GMSB models. Initial state radiation corrections take into account PT/PL effects in the Structure Function formalism, and an optimised hadronisation interface to JETSET 7.4 including final state radiation is also provided.