The in vitro inhibition of 412 cultures of Salmonella by streptomycin was studied. All of the recognized types in the genus were included in the work. Of the commonly occurring types, S. paratyphi A and S. typhi were the most sensitive, while S. pullorum and S. enteritidis were somewhat less susceptible. The remainder of the types which are found frequently was more resistant. The majority of the types required 2-4 times as much streptomycin to inhibit growth as did Escherichia coli W. Different cultures of the same type often varied widely in their susceptibility to streptomycin.