International meetings on various aspects of cancer- its etiology, its diagnosis, its treatment, its palliation, and its prevention and control are held frequently. Many have similar themes, and many seek and receive the same speakers and audiences. A fundamental question arises: what difference does any individual meeting/congress/conference make or add to our understanding of the relevant issues? While many meetings conduct evaluations at the end of the Congress, few use evaluation as a tool to guide design, implementation, and evaluation of both short and long term impacts, and address the question of "what difference did the Congress make". The International Cancer Control Congresses, which are held biennially in different regions of the world, took the opportunity to use evaluation in this way, and ask the relevant questions. This paper describes that evaluation session of the ICCC4, held in Seoul, Korea in November 2011, which was part of the larger evaluation issue.