Streptomycin need not be administered in large amounts, four to eight daily doses, totalling 1 to 3 grams a day for three to six months, to elicit a favorable response in the treatment of tuberculosis. Such a frequent, heavy and prolonged regimen is likely to injure the patient and leads to the emergence of resistant organisms which render further use of this agent futile. The minimal effective dose is about 0.2 grams a day, or 4 milligrams per Kg., and double this amount offers an adequate factor of safety. Two grams of streptomycin given only once a week or 1 gram twice a week, is not only less toxic, but is less rapidly followed by the development of resistant bacilli. Combinations of streptomycin with collapse therapy and with para-aminosalicylic acid, or other chemotherapeutic agents, still further conserve its efficacy and extend the indications for its use.