Chakaria Health and Demographic Surveillance System (CHDSS), located on the south-eastern coast of the Bay of Bengal, was established in 1999 and is one of the field sites of International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDRB). The surveillance covers 118 315 residents living in 19 847 households. Data on socio-demographic and health indicators including birth, death, migration, marriage, maternal health, education and employment are recorded through quarterly household visits. The primary objective of CHDSS is to monitor the changes in socio-demographic indicators, inequalities in health and impact of public health interventions. A demographic change was accompanied by a shift from traditional to modern society during the past decade, but inequality in health still persists. The findings from the surveillance are shared regularly among the local and global communities. Data are also available upon request to ICDDRB and INDEPTH for use by researchers and policy makers.