- Background: Army personnel, albeit in general young and healthy, are at greater risk for infectious morbidity owing to higher crowding, compromised hygienic conditions, and exposure to new geographic and climatic factors. We describe the changing trends in the incidence of major infectious diseases of public health importance in the Israeli military: hepatitis A, measles, meningococcal disease, and diarrheal diseases. Methods: Departments of Epidemiology and Medical Statistics of the Israel Defense Forces Medical Corps monitor the incidence of infectious diseases within the military. Notifiable diseases are predefined and their reporting is mandatory. Results: The incidence of hepatitis has declined significantly since the introduction of prophylaxis with immune serum globulin in the 1970s, and complete control of outbreaks has been achieved. Outbreaks of diarrheal diseases have decreased, probably as a result of intensive control measures begun in the last decade. However, sporadic diarrheal morbidity continues to rise. The vaccination of recruits against Neisseria meningitidis was begun in 1994, following an increase in cases caused by serogroup C bacteria. So far, the program has proved efficacious in reducing morbidity. Measles morbidity in the military was much higher than in the civilian sector over the years. It has become negligible since 1995, when the first cohorts with 2 vaccination doses began their service. Conclusion: Despite improvements in personal and environmental health measures, immunization remains the most efficient means for preventing infectious diseases in the military.