In the early 2000s, syndromic surveillance emerged in Europe in response to the emergence of health phenomena for which existing systems were ill-suited or inadequately adapted. With the ultimate goal of improving the ability to detect and monitor the impact of these events on human and animal public health at the European level, the European Triple-S project (Syndromic Surveillance Survey, Assessment towards guidelines for Europe), co-funded by the European Union’s Executive Agency for Health and Consumers and bringing together 24 organizations from 13 countries, was launched in 2010 for a three-year period. This article presents its main findings. Based on a common definition of syndromic surveillance developed with the project partners, two inventories identified 33 systems in 15 countries in human health and 27 systems in animal health across 12 countries. Eight site visits provided deeper insight into the main characteristics of certain systems. Based on the knowledge gained and the experience of the project partners, practical guides were produced to help European countries develop or improve their own syndromic surveillance systems. At the end of the three-year project, a strategy for organizing national and European stakeholders was proposed to ensure a joint analysis of the results from European syndromic surveillance systems. This strategy outlines the future steps for European cooperation in this field. (R.A.)