An experimental model of cavitary tuberculosis in the animal was used, induced in rabbits, guinea-pigs or rats, and the effect of three therapeutic regimens was followed, that contained the tuberculostatics listed below: -- INH + RMP + protinamide (I); - INH + RMP + SM (II); - INH (III). In the animals that were sacrificed periodically a quantitative evaluation was made, by seeding of organ samples in culture media, of the dynamics of bacterial populations isolated at 1, 3 and 5 months after the start of the treatment. The best results were obtained with the therapeutic regimen nr. II. The association of INH to RMP leads to a rapid decrease in the number of germs. The complete recovery of the animals however was not obtained, according to histological and bacteriological criteria.