It is almost thirty years since the nations decided that the World Health Organization should be founded as the single agency for directing and coordinating intergovernmental health activities. Subsequent developments have been very fully documented in two WHO publications respectively on the first and second decades of the Organization's existence and in the series of annual reports that started in 1948. But WHO did not come into being as a result of some process of spontaneous generation. As it exists today, it represents the culmination of over 120 years of strivings, at first with very limited objectives, towards intergovernmental cooperation in understanding and solving health problems. For theJirst four decades, international agreement was frustrated by lack of scientijic knowledge. Since then, every gain to knowledge won by medical research has increased the possibilities of fruitful international cooperation far the benefit of all mankind.