The recent licensing of active hepatitis A vaccines raises the question of vaccine candidates. Although various groups of workers are at theoretical occupational risk of hepatitis A infection, no comprehensive quantitative data exist to determine which occupational groups should receive active vaccination. Therefore, the aims of this study were to identify occupations at risk for hepatitis A infection and to determine their relative risk. In this nationwide historical prospective study, the relative risk of hepatitis A among different occupations in Israel was determined according to the incidence of hepatitis A in different occupations during 1993 and 1994 compared with the incidence of hepatitis A in two standard populations. After age, gender, ethnicity, and time of immigration to Israel were controlled for, certain occupations showed a significant increased risk of hepatitis A: yeshiva students (standardized incidence ratio (SIR) = 9.98, 99% confidence interval: 7.55, 13.18), day care center and kindergarten staff (SIR = 5.47, 99% confidence interval: 3.50, 8.57), food industry workers (SIR = 5.41, 99% confidence interval: 1.92, 15.25), teachers (SIR = 4.02, 99% confidence interval: 2.92, 5.48), physicians and dentists (SIR = 3.77, 99% confidence interval: 1.78, 8.14), and therapists and medical technicians (SIR = 3.75, 99% confidence interval: 1.75, 8.14). Sewage workers and nurses did not show any significantly increased risk. The results were validated by comparison with an additional standard population. This first nationwide study identified occupations at risk of hepatitis A infection. It emerged that the authors' approach can provide a yardstick for measuring samples in both large and small countries that have a socioeconomic background similar to that of Israel.