The Chi Linh Health and Demographic Surveillance System (CHILILAB HDSS) is the only health and demographic surveillance system (HDSS) in an urbanizing area of the Chi Linh district of Hai Duong, a northern province of Vietnam. It is one of the few field laboratories in the world that links operational research and health interventions with field training. The CHILILAB HDSS provides longitudinal data on demographic and health indicators for the community of Chi Linh. In 2012, when the CHILILAB HDSS included 57 561 people from 17 993 households in 3 towns and 4 communes, it used structured questionnaires to collect information on population changes (birth, death, migration, marriage, and pregnancy) in the community. As of December 2012, 5 rounds of a baseline survey and 17 periodic update surveys or re-enumeration surveys had been conducted. In addition, several specialized public-health research projects, focused particularly on adolescent health, have been implemented by the CHILILAB HDSS. The information that the CHILILAB HDSS has gathered provides a picture of the health status of the population and socio-economic situation in Chi Linh district. The contact person for data sharing is the director of the CHILILAB (E-mail: thb@hsph.edu.vn).