Abstract: Savitskaya and Kartsava have recently reported that streptomycin gave yellow color reaction with 2,4-dinitrophenyl hydrazine, forming hydrazone, and the reaction may be employed for colorimetric determination of streptomycin. The authors propose a modified procedure outlined below: To 10 ml of sample solution of streptomycin add 0.5 ml of 2,4-dinitrophenyl hydrazine reagent, heat the mixture at 80℃ on water bath for five minutes and then extract four times with amyl acetate to remove the excess of reagent. Determine the optical density of the aqueous solution at 430 mμ using distilled water as blank. The concentration range of best accuracy of the modified method was found to be 65-200 units/ml.