The authors have carried out some modifications of the formula of the Löwenstein-Jensen medium in view of a better cultivation of the Koch bacilli. The changes consisted in the elimination of glycerin, addition of glucose, or sodium pyruvate and glucose, or in the addition of fractions of cultures of mycobacteria. The material seeded on this medium consisted in 20 wild strains of tubercle bacilli (M. tuberculosis) showing both drug sensitivity and drug resistance, and 167 samples of sputum obtained from patients with confirmed tuberculosis or from subjects suspected of tuberculosis. The possibility to identify the effects of sodium pyruvate and of glucose by increasing their concentration to 0,5 g% was also studied with another 68 products. The results demonstrated that addition of 0,25 g% of sodium pyruvate, and of 0,25 g% of glucose, as well as elimination of glycerin from the Löwenstein-Jensen medium stimulated the development of the Koch bacilli from pathological products, and increased the frequency of positive cultures. The development of colonies 1 to 2 weeks earlier and the obtention of more numerous eugenic colonies.