Character of epidemiology process of tubercular infection depends on a volume and quality of prophylactic measures among which a chemoprophylaxis has decisive importance. To study of quality and efficiency of a chemoprophylaxis, an analysis was made 150 children case history, from them 98 lived in nidus of tubercular infection. It’s marked that absence or off-grade conducted and organized a chemoprophylaxis (by an out-of-control method, traditionally by one chemodrug, without the account of all risk factors), promotes the risk of development of local tuberculosis at children, resident in the nidus of tubercular infection.