International meetings on various aspects of cancer- its etiology, its diagnosis, its treatment, its palliation, andits prevention and control are held frequently. Many have similar themes, and many seek and receive the samespeakers 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 evaluationsat the end of the Congress, few use evaluation as a tool to guide design, implementation, and evaluation ofboth short and long term impacts, and address the question of “what difference did the Congress make”. TheInternational Cancer Control Congresses, which are held biennially in different regions of the world, took theopportunity to use evaluation in this way, and ask the relevant questions. This paper describes that evaluationsession of the ICCC4, held in Seoul, Korea in November 2011, which was part of the larger evaluation issue.