The "nosocomial infection" is limited to describing infections that acquired in hospitals, while the "healthcare-associated infection" (HAI) generally refers to infections that patients acquire while receiving treatment for medical or surgical conditions. HAIs may occur in all settings of care, including hospitals, long-term care facilities, homecare facilities, or outpatient departments. In order to respond to continuous evolving in the contents of medical services and the expansion of surveillance range, "healthcare-associated infection" instead of "nosocomial infection" was commonly used internationally as well as in the definition of infection surveillance in the acute care settings that published by the US CDC in 2008. Taiwan CDC had launched the Taiwan Nosocomial Infections Surveillance System (TNIS System) in 2007 and revised to Taiwan Healthcare-associated infection and Antimicrobial resistance Surveillance System (THAS System) in 2020 to monitor the occurrence of HAIs effectively, to evaluate the epidemiologic trend of HAIs in Taiwan, and to analyze surveillance data using well-recognized indicators. All the information could be made use of collectively to serve as important references for policy making. Besides, strengthening functions and the utility of the surveillance system is continuously going on. THAS system not only gather demographic data of HAI case and patient-specific cultures and antimicrobial susceptibility results from reporting hospitals, but also provides format report functions for reporting hospitals and policy makers to analyze data locally and nationally as a reference in developing quality improvement initiatives.