Legionnaires' disease and Pontiac fever are both diseases with important public health implications and require prompt and thorough responses to outbreaks for future prevention. Effective methods for defining, diagnosing, reporting and responding to legionellosis outbreaks ideally should be standardized across countries. Therefore, the European Union surveillance methods for countering Legionnaires' disease is a useful model especially for travel-associated Legionnaires' disease (TALD) cases which are on the rise. Multi-country surveillance in the EU and European Economic Area (EEA) has evolved since the first organizational efforts in the 1980's to the currently responsible, European Legionnaires' Disease Surveillance Network (ELDSNet). This chapter outlines the practices of the EU surveillance of Legionnaires' disease including their schemata, definitions, responsibilities of participating members, methods and the results of the data collected since the program's inception. Lastly, improvements must still be made as the incidence of Legionnaires' disease in the EU is likely underestimated due to underreporting and/or underdiagnosis. Nearly 70% of cases are reported from only four countries, France, Germany, Italy and Spain, which represent 50% of the EU population.