We have entered the era of simulator-based Mission Rehearsal (MR). The capability will soon exist to provide real world mission rehearsal and practice to mission qualified aircrews before they leave the ground. The engineering capability to provide MR will undoubtedly improve as time goes on. However, a variety of behavioral issues need to be addressed before we will be confident about effectively using this new technology for training or practice purposes. In this paper we list and discuss some of those issues with the goal of setting forth a research agenda. Plans for MR research, at the Operations Training Division of the Air Force Human Resources Laboratory are described.