The good results gotten employing short-term (6 months) medication regimes with rifampin, isoniazid and an initial supplement (2 months) of streptomycin and pyrazinamide, gave an impulse to pharmacodynamic research. Some recent studies divided bacterial population into four groups, according to bacterial growth time and they showed that rifampin, isoniazid and streptomycin act on mycobacterial groups continuously or intermittently growing. This fact confirms the validity of employed therapeutic regimens. An other paper considered the trend of hematic levels of streptomycin, isoniazid, rifampin and pyrazinamide. The results of this study showed that the variations observed in hematic peaks were independent from the administered doses and from the administration way. These researches help in solving the most important problems of present tubercular chemotherapy, such the use of a single drug or the therapy interruption.