The natural history of tuberculosis was re-examined, and especially the relation between contagion and first infection on one side and, on the other, primary tuberculosis (in children) and secondary tuberculosis in adult. With regard to the primary tuberculosis, the different clinical pictures were taken into consideration and it was reported how symptoms change as years go by (see miliary tuberculosis). As for the diagnostic aspect the importance of a quantitative interpretation of Mantoux reaction, was emphasized. In the final judgement, all factors that may change the results can therefore by considered: from the intercurrent viral infection to the patient's age, to the spreading of atypical mycobacteria in that area. The screening performed with the multi-injections technique is necessary to control the diffusion of the infection in the general population. In Italy, 1-2% of children aged 6 to 14 years old, are skin positive but the percentage varies widely in the different areas. However, it was higher than that observed in other European countries and far from the 1% incidence for 14 year olds, as hoped by the World Health Organization. After re-examining the characteristics of the four most important anti-tubercular drugs with particular attention to possible hepatotoxic effects of the isoniazid-rifampicin association, the authors analyses new therapeutic strategies, especially the one that tends to shorten treatment periods. This approach is effective in adults but has not yet been definitively confirmed in children. The surgical approach is more standardized in superficial adenitis where extirpation is indicated in atypical mycobacteria infections rather than in those due to Koch's bacillus. As far as indications of chemoprophylaxis are concerned it would seem that an international arrangement has now been reached that on the whole extends the indications to this type of treatment. The only uncertainty is whether adults, with intradermal reactions to tuberculin should undergo chemoprophylaxis if the time of contagion is unknown and the subject does not show any particular risk factors. On the grounds of data from literature, the results of vaccination are contrasting. Many factors could be responsible for this, especially the use, till a few years ago, of a non-standardized vaccine. However, vaccination remains an efficient method in populations at risk, listed in Italian law too. Nevertheless, according to the law, the subjects who would most benefit by vaccination are excluded (children under the age of 5 years and over the age of 15 years). However vaccination is getting less important in the general population.(ABSTRACT TRUNCATED AT 400 WORDS)