The Bhattacharya method (decomposition of frequency distribution into Normal components by a graphic method) was applied to 35.680 results of tuberculin tests performed on the persons who demanded the Health Centre of Ribeirão Preto, between May-1973 and April 1974. It was possible to evidence, to characterize and to show three Normal components (corresponding to uninfected, probably infected with atypical strains of mycobacteria and infected with mycobacteria) in diferent age groups. There is a possibility of misclassification in the kind of reactor in the tuberculin test, since the anonymous strains of mycobacteria are presente in the geographic area.
Atypical bacterials forms; Misclassification; Tuberculin test
