New evidence is presented in support of the hypothesis put forth by Camba et al. [1] that streptomycin enters bacterial cells by a process of active transport. In this paper a general inhibitor of transport, uranyl nitrate, when added to the bacterial suspension prior to the addition of streptomycin, was shown to significantly increase the resistance to the drug. Furthermore, in suspensions of cells with a progressively exhausted endogenous metabolism and consequently with less available energy, a corresponding increase in the amount of streptomycin remaining in the supernatant was observed.