Immunogenicity of four substrains of BCG was studied in mice vaccinated by the intravenous route and evaluated through pulmonary density and through splenic, hepatic and pulmonary indexes (weight of the organ/weight of the animalx100). In addition, tuberculin sensitivity was determined by measuring the thickness of the inoculated leg. All four strains (BCG Brazil, BCG Prague, BCG Russia and BCG Glaxo) showed intermediary virulence (0.78 -- 0.85) between pathogenic mycobacteria, i.e., M. tuberculosis and non-pathogenic mycobacteria, such as M. fortuitum, without however revealing differences among themselves in regard to pulmonary density. Reinoculation of vaccinated animals by the intravenous route, contrary to the subcutaneous route, resulted in significant increase (P less than 0.05) in the organs, except for the spleen. The tuberculin hypersensitivity induced by the four strains was significant and it was possible to distinguish BCG Brazil from BCG Glaxo. The substrain BCG Brazil proved to be the most immunogenic, followed by BCG Prague, whereas BCG-Glaxo proved to be the weakest vaccine.