Sera from 872 healthy subjects among the Jewish population of Israel were examined for antibodies to varicella zoster virus (VZV) by a simplified technique for the detection of immunofluorescent antibody to membrane antigen. The difference in the geometric mean titer of antibodies to the virus among the the different age groups was highly significant (P less than 0.0001). The highest titers were found in the five-to-seven-years and 21-to-30-years age groups. In 211 subjects, aged 17 to 40 years, the antibody titres were not influenced by sex or ethnic origin. The percentage of seronegative subjects (titer less than 2) was relatively high--between 18.7 and 32.9% in the 21-to-60-years age groups--and it was 19.5% in the population of childbearing age. The importance of screening for VZV immune status in pregnant women is emphasized.