International joint development programs are important because of their potential to reduce costs and increase partnership benefits such as interoperability, economies of scale, and technical advancement. While all major development and acquisition programs are complex undertakings, international joint development programs introduce additional layers of complexity in the requirement for coordination with more than one government customer, supply chain and organizational complexities resulting from international industrial teaming, and technology control issues. The performance of international joint development programs varies greatly. This study compares the best practices of international joint development and domestic development programs through case-study analysis to identify the key variables that contribute to a program’s eventual success or failure and to understand the elements that are crucial to managing these programs.