The Butajira Health and Demographic Surveillance System (HDSS), hosted by the School of Public Health at Addis Ababa University, operates in one urban and nine rural kebeles located in the Meskan, East Meskan, Mareko, and Silti districts of the East Guraghe and Silti zones in central Ethiopia. The surveillance population was initially selected using a probability proportional to size (PPS) sampling approach, covering approximately 10% of the total population in the districts. The system began with a baseline survey conducted in 1986-87, followed by monthly household visits to record vital events such as births, deaths, marriages, and migrations. This baseline survey informed a comprehensive household census, which served as the foundation for a dynamic cohort surveillance system established on January 1, 1987. Currently, the HDSS monitors a population of 63,460 individuals. To ensure data quality and validity, comprehensive censuses are conducted every five years. Based on insights gained from Butajira and similar surveillance sites, the data collection schedule was revised from monthly to quarterly updates following the 1999 census. These quarterly surveillance rounds are conducted by locally recruited Resident Enumerators (REs), who live within the kebeles they serve and are responsible for collecting data on vital events using standard modules: birth, death, in- and out-migration, marital status changes, individual membership, family composition, and household characteristics. Additionally, the HDSS collects cause of death data using the WHO 2014 Verbal Autopsy (VA) instrument.