With the decrease in tuberculosis, local microepidemics of tuberculous infection and disease have been described, specially when the annual risk of tuberculous infection, is less than 0.1%. This phenomenon is more frequent in school children when they are exposed to a potent infectious source case. 13 epidemics in school children who had been in contact with one or two highly contagious tuberculous cases (teacher or pupils) are shown. Prevalences of infection as high as 97% are found among the exposed children and their risk increases to 5.7. The tuberculin convertors are 37.9% and their risk increases to 16.7. Treatment recommendations are indicated, they include avoidance of massive unselected prospections and the need of adequate collaboration. BCG vaccination increases the difficulty in the search of infected persons and group infections.