The nations of the world spend a signifi cant portion of their wealth on militaries. Every year,billions of dollars go to recruiting, training, maintaining, and equipping the men and women who serve their countries in uniform. This paper looks into one aspect of military spending, acquiring new equipment and systems. In particular, the research focuses on international cooperation in weapon system development and proposes a model to aid decision makers to decide whether and when to join a joint development program. The main goal is to determine what factors are most important in choosing military acquisitions program partners and then to create a model using those factors that will produce policy recommendations for program cooperation.