Some primate field studies have been on-going for decades, covering significant portions of individual life cycles or even multiple generations. In this volume, leading field workers report on the history and infrastructure of their projects in Madagascar, Africa, Asia and South America. More importantly, they provide summaries of their long-term research efforts on primate behaviour, ecology and life history, highlighting insights that were only possible because of the long-term nature of the study. The chapters of this volume collectively outline the many scientific reasons for studying primate behaviour, ecology and demography over multiple generations. This kind of research is typically necessitated by the relatively slow life histories of primates. Moreover, a complete understanding of social organization and behaviour, factors often influenced by rare but important events, requires long-term data collection. Finally, long-term field projects are also becoming increasingly important foci of local conservation activities.