Streptomycin sulfate was entrapped in liposomes obtained from lecithin by a detergent method at the ratio of 250-300 mcg streptomycin-base per 1 mg of lecithin. Intravenous injection of liposome-entrapped streptomycin (LES) to the mice infected with Mycobacteria tuberculosis H37 Rv led to a statistically significant decrease in the spleen mycobacterium number, but not in the lungs, as compared to the buffered solution of streptomycin (SS). Intravenous treatment of the mice with LES resulted in prolonged mouse survival, as compared to that with SS. Acute streptomycin toxicity was also reduced by its intravenous administration in the form of LES.