BCG vaccination programmes were introduced into Czechoslovakia 40 years ago under a quite different epidemiological situation than that of today. Compulsory mass BCG vaccination of infants born in a selected area was discounted in 1986, except for those having a high risk of contracting tuberculosis or those whose parents expressly asked for it. The aim of this study was to ascertain the risk of tuberculosis infection and breakdown rate from infection to disease in 165,854 newborns following a period of 6 years. The average risk of infection in children aged 0-6 years was low (0.046%). No identifiable factors increasing the risk of infection were found. Primary tuberculosis was diagnosed in 31 children (7/100,000 persons/year); this corresponds to a 15.5% breakdown rate from infection to disease. The majority of patients were symptom-free with minimal disease and detected in the course of regular check-ups. These findings indicate that the change from mass BCG vaccination to selective vaccination of high risk newborns can be recommended. Nevertheless social and economic aspects which involve migration, living conditions and the attitudes of the population, as well as of medical staff, to vaccination should also be taken into consideration.