Since the end of the Second World War Papuans and New Guineans have been rapidly adopting the pattern of European civilization. Striking socio-economic changes have been accompanied by changes in diet, a significant reduction in infant mortality and, most importantly, an expansion in the population. The changes are not uniform in all parts of the Territory and it is possible to find and study people in all stages of development. The United Kingdom/Australian project involved multi-disciplinary studies of two contrasting populations. The first, on Karkar Island, lives in a hot, humid climate and consists of indigenes who provide most of the labour for the coconut and coffee plantations; they have had access to European food and goods for nearly 50 years but the diet and housing is still primitive. Labourers have also been imported from the highlands of New Guinea and have been subjected to the hazards of malaria and tuberculosis for the first time. The second population, at Lufa in the eastern highlands, is largely a subsistence population in a more primitive state. It has more recently been introduced to European food and goods and is less affected by European habits. The climate is less rigorous at an altitude of approximately 1700 m and malaria, hookworm and tuberculosis are not serious problems.