After the Invasion of Kuwait in 1990 Kazem Behbehani had to flee Kuwait and joined the WHO. At WHO (1990–2005), he worked in the vaccine research of the Global programmed of AIDS, was the Programme Manager of Tropical Disease Research (TDR), the Director of both the Division of the Control of Tropical Diseases (1994–1998) and, the Eastern Mediterranean Liaison Office (1998–2003) in Geneva. He served as a member of the WHO Board of Appeal, Secretary of number of Intergovernmental meetings (e.g. Tobacco Convention), as well as several of the committees/subcommittees of the Executive Board and the World Health Assembly. His last position was Assistant Director-General for External Relations and Governing Bodies (2003 - 5). In 2005, he became WHO Envoy. In 2006 he became official candidate in the WHO Director General election, where he succeeded to reach the top 5 list.