The A. makes considerations on the technique of preparing tuberculins and reports the method which he uses at the Instituto oswaldo Cruz. This method consists in the use of Koch's bacillus strains both of human (Ratti) and bovine type (Vallée) cultivated on Dorset's medium slightly modified. This medium was that which afforded better results as compared with others experimented by the A. As to the verification of the tuberculin activity, the A. examines the various methods employed and gives the preference to be method of comparison with a standard tuberculin, by means of Von Pirquet's reaction, in a group of adult individuals, taken indiscriminately.