Rifampicin has been widely hailed as the most effective antituberculosis antibiotics since the clinical use of streptomycin, but its immunosuppressive side effect was still annoying problem to be excluded. These studies were carried out to determine the effect of Tuberein-3, tuberculous bacilli extraction with water, on Rifampicin induced T-lymphocytopenia in 5 cases of pulmonary tuberculosis who have never exposed to antimetabolites or steroid compounds.