Background: The epidemiology of chickenpox in Israel is changing, mainly due to the increasing - but not universal - uptake of varicella vaccine. Patients and Methods: We conducted a seroprevalence study of varicella zoster virus (VZV) antibodies among 536 Israeli military recruits 18 years of age, on the basis of a representative sample of sera collected in 2003. Results: The overall seroprevalence rate was 94.6%, which was significantly lower than that observed in a similar population in 1992 (98.4%, p < 0.001). The rate was lower among subjects whose fathers had less than 12 years of schooling (89.8%, p = 0.033). No statistically significant differences were observed when data were stratified by sex, subject's level of education, or origin. Conclusion: This decline in the level of immunity must be considered when determining pre- and post-exposure vaccination policy among young adults in crowded environments.