Observations of the 58th Special Operations Wing (58 SOW) Weapon System Trainer/Mission Rehearsal System (WST/MRS) during rehearsals have clearly shown that mission rehearsal (MR) effectiveness is influenced by the activities of both the people who support the MRS and the people who use it. To explain this demonstrated importance of the people involved in MR, a human activity system model of simulation-based rehearsal was developed. It provides an integrated depiction of the MRS, and specifically addresses: (1) the context for rapid database development and simulation-based MR (crisis action planning) and how the MRS fits into it; (2) MRS components, functions and structure; and (3) processes that enhance rehearsal effectiveness. Implications of this human activity system view are discussed, including: places in the mission preparation process where simulation can benefit operations; the scope of human activities that are essential for successful simulation-based MR; the potential value of MR to provide feedback concerning the adequacy of training to support mission requirements; and the need for new procedures throughout this extended scope of players to accommodate both MRS requirements and capabilities.