Since 2005, there has been a steady decline in the incidence rate of Legionnaires' disease in France. In 2010, with 1,540 cases, there was a 28% increase in the number of cases compared to 2009, representing an incidence rate in metropolitan France of 2.4 per 100,000 inhabitants. The increase was most pronounced during the months of August and September and in the eastern regions of France. The median age of cases was 62 years, the male-to-female ratio was 3.2, and the case-fatality rate was 11.7%. The majority of cases were diagnosed via a urine detection test, and a strain was isolated in 282 cases (18%). Risk exposure was reported for 34% of these cases. No outbreak (more than 10 cases) was identified in 2010. This summary of Legionnaires’ disease cases from 2010 shows that the downward trend observed in recent years has reversed. Additional studies are underway to document this increase. Rapid and systematic investigations likely limited the number of clustered cases but did not, however, identify the sources of contamination for these outbreaks. It is therefore important to maintain awareness among all partners in order to document the characteristics of contamination sources and thereby improve control of this disease through the rapid implementation of control and prevention measures. (R.A.)