A web-based hospital-acquired infection surveillance system (WHISS) was implemented in a 2200-beds medical center in Taiwan. Clinical data from hospital information system, laboratory information system and others were collected and analyzed. The hospital-acquired infection decision guidelines of WHISS utilize this information to detect 9 patterns of defined hospital-acquired urinary tract infection. Moreover, these data were integrated into a signal entry point user interface to assist physicians and healthcare providers in making decision. We use web services techniques based on Service-Oriented Architecture (SOA), which are suitable for integrating heterogeneous platforms, protocols, and applications. The WHISS detects 81.9% candidates of hospital-acquired infection event in real time and provides user-friendly interface to infection control nurses. In conclusion, the WHISS simplifies the workflow of hospital infection control, and improves the heaIthcare quality.