In this study, the effect of catalase on the rate of growth Mycobacterium tuberculosis has been investigated. Thirty-five sputa were inoculated on the Löwenstein-Jensen medium and Löwenstein-Jensen medium modified by the addition of catalase 4 mcg/ml. Only four sputa were observed to have an early growth on the Löwenstein-Jensen medium with catalase five days than Löwenstein-Jensen medium. Of the 55 strains grown in the Löwenstein-Jensen medium the following results were obtained from the inoculations made in the Löwenstein-Jensen with catalase and Löwenstein-Jensen medium. At the end of a three week incubation in a medium with 5-10% CO2, a growth of 32 strains (58%) in the Löwenstein-Jensen medium with catalase and a growth of 21 strains (38%) in the Löwenstein-Jensen medium were observed Eleven strains (20%) were observed in the Löwenstein-Jensen medium with catalase and B strains (14%) in the Löwenstein-Jensen medium during the same time in normal atmosphere.