Introduction – Objectives: To determine the serological status of the population of metropolitan France aged 6 to 49 years with respect to 10 infectious diseases. We present the results for five vaccine-preventable diseases: measles, mumps, rubella, chickenpox, and hepatitis A. Materials and Methods: Patients were enrolled from September 2009 to June 2010 during blood draws conducted at 124 laboratories selected at random following a two-stage survey, stratified by region and laboratory activity volume. Serological testing was performed by a single laboratory. The analysis was conducted in accordance with the sampling plan. Estimates were adjusted for patients’ age, sex, and region of residence. Results: 5,300 patients were included, of whom 45% were aged 6 to 19 years, 28% were aged 20 to 29 years, and 27% were aged 30 to 49 years. The estimates of the proportions of susceptible individuals for measles, mumps, and rubella were 8%, 13%, and 6% among those aged 6–9 years; 7%, 13%, and 8% among those aged 10–19 years; 8%, 13%, and 8% among those aged 20–29 years; and 2%, 6%, and 5% among those aged 30–49 years. Regarding HAV, 6%, 21%, and 39% of individuals aged <20 years, 20–29 years, and 30–49 years, respectively, were seropositive. More than 95% of individuals were seropositive for varicella. Conclusion: The persistence of a high proportion (= 6%) of susceptible individuals to measles, mumps, and rubella among those under 30 years of age, a consequence of insufficient vaccination coverage, explains the current measles epidemic and suggests a risk of circulating rubella and mumps viruses. A comparison of the results for HAV with those of a similar survey conducted in 1998 shows a decrease in seroprevalence, particularly among those over 30 years of age (39% vs. 57% in 1998).