This paper explores the role of World Health Organization (WHO) medical experts in ambitious projects for substance control during the Cold War in Thailand and India. The circumstances surrounding opium production in these two nations were very different, as were the reasons for requesting expert assistance from the United Nations. Whereas the Thai military regime was concerned with controlling illicit traffic to secure its borders, the Indian government wanted to direct its opium raw materials towards domestic pharmaceutical production. Overlapping and sometimes competing agendas of country governments and international agencies converged upon each project, complicating the consultants' work and requiring careful navigation. In both cases, medicine as a science concerned with human health and well-being was subordinated to more pressing agendas. At the same time, the article argues that WHO consultants left an important impact, though not necessarily due to their skills and training in medicine. Instead, they provided exemplars of sound governance and delivery of public health in a politically stable and economically developed country.