The medical surveillance program for animal caretakers, technicians, and other personnel having contact with animals at the National Institutes of Health is described. The program classifies workers according to the groups of animals with which they work. It includes preplacement physical examinations, preventive immunizations, testing, and monitoring of health status. This program helps to protect the workers' health from diseases acquired from animals and to prevent ill employees from adversely affecting the health of the animals with which they work.