Epidemiological danger of tuberculosis foci with patients suffering from active and inactive tuberculosis was studied. For this purpose 151 children being in contact with tuberculous patients were examined. The control group included 300 children from healthy surroundings. The study showed that the immunity levels in the children from the tuberculosis foci were lower and tuberculin sensitivity by the Mantoux test, the infection rate and tuberculosis incidence in them were higher than those included 300 children from healthy surroundings. Since the infection rate in the children from the foci with patients suffering from inactive tuberculosis was high it was considered necessary to subject them to sanation including chemoprophylaxis in accordance with the medical indications.