The title of this supplement is that chosen for the Eighth Congress of the International Federation of Psychiatric Epidemiology, held in Taipei, Taiwan, on 6–9 March 1999 and co-sponsored by the Institute of Biomedical Sciences, Academia Sinica, and the Taiwanese Society of Psychiatry. In addition to the Federation's main aim of encouraging population-based research in different world regions, and especially in developing countries, the Taipei Congress was intended to improve communication between disciplines that in general still pursue such research quite independently of one another. The papers included here represent a small part of the scientific programme, selected for their special relevance to the central topic of the meeting.