This Note is a nontechnical description of the Dynamic Retention Model (DRM), which facilitates analyses of the costs and benefits of proposed changes in the major policies affecting military personnel, including the level and structure of military compensation, the major parameters of the personnel system, and the nondisability retirement system. The DRM predicts a retention rate for a group at any particular point that depends both on future prospects and on history (promotions, pay, bonuses, etc.) for the group members. Because it models individual decisionmaking, the model can simulate the effects of policy changes that have no analogues in past policies. The authors demonstrate the flexibility of the model by comparing it with the Annualized Cost of Leaving model.