Two rural communities in Papua New Guinea, the Wopkaimin, which experienced massive socioeconomic development through the Ok Tedi Mine Limited (OTML) commencing in 1983, and Mt Obree, which was without any major economic project during that time, were followed annually since 1982. 83 variables including births and deaths were monitored. The crude birth rate (CBR) and infant mortality rate (IMR) were high in both areas at the beginning. IMR decreased significantly among the Wopkaimin only. The Wopkaimin’s CBR increased immediately after mining but declined later, with no significant change in Mt Obree. The influence of various socioeconomic, cultural and environmental factors is discussed. Demographic monitoring at the community level is accurate, economical and reproducible.