With the aim to produce the KOCH's phenomenon, the A. A. incoulated 30 lepers of the Colonia Mirueira (Recife), from various ages and clinical types, with alive suspensios of three strains of acid-fast bacilli isolated from lepers. Each volunteer received three intradermical inoculations in his thighs, of 0.2 c.c. each from strains "Chaves II", "Emília", and "Hecke" and in his left forea rom 0.2 c.c. of Leprolina S.A. (killed antigen). At the 10th day of inoculation were verified that 24 out of the 30 volunteers had severe general reaction, 2, moderate ones and 4, nothing. 16 out of the 30 had leprosy reaction, being 10 lepromatous cases and 6 inactive oens. The inoculum "C II" produced craters, of 1 x 1 and 2 x 2 cm. diameter in the 30 patients (total), craters with complete destruction of the skin; the inoculum "E" did the same in 29, of equal severety and the inoculum "H" did only in 23, but lesions of minor severety and the "L" produced craters in ten patients, evidently due to the concomitant action of one of the three inocula. At the same 10th day were inoculated secretions onto 20 tubes of LOEWENSTEIN medium of seven patients. 18 days later were seen developpment of retrocultures in 19 ou 20 tubes, the mojority being contaminated by fungs or cyanophile bacteria. From one patient (nº 16) was recovered a chromogenic culture from his Leprolin-test, macro and microscopically undistinguishable from strain "C II" or "E", which, based on a large experimentation the senior writer is inclined to consider as identical. At the 18 th day were made smears from lesions of 13 patients, 30 in total with 15 positive (50%) for one or another of the inocula. The macro and microscopical morphologies of the recovered cultures (retrocultrues) coincide with the characteristics of the original cultures from which the inocula were made. In conclusion, the majority of the patients showed partial or integral KOCH's prenomenon, with its classical general, local and focal reactions. By lack of laboratory resource, at the leper Colony, the precious material available from this series of experiments were not used, resulting in omissions of various kind in this paper.