The purpose of this study was to determine the proportion of day care workers susceptible to Varicella-zoster virus (VZV) in local day care centers and to compare these data to susceptibility rates in other adult populations, mainly hospital personnel. A total of 545 serum samples were obtained from 494 day care workers in the Alabama metropolitan area. The workers were predominantly white and female, and over 60% were either currently or previously married. Of these 545 subjects, 95.2% were seropositive for VZV antibody and 4.8% were seronegative. Of the workers completing the questionnaire, 31% were uncertain of the disease history. Among the 151 workers giving an uncertain history of VZV infection, and four were seronegative. Of the workers giving a negative history of primary VZV infection, eight of the 59 were in fact seronegative by assay. The authors conclude that in this population, the proportion of day care workers susceptible to VZV was relatively small.