This clinical trial will compare the effectiveness of streptomycin, which historically is the standard drug for treatment of plague, with gentamicin. The hypothesis is that gentamicin is not inferior to streptomycin but that it will have less severe side effects. The study is being done in Madagascar because that country reports the most plague cases in the world. Patients coming into a participating clinic with suspected plague (bubonic, pneumonic, or septicemic) will be randomized into one of two treatment arms after giving informed consent. Patients will be monitored for side effects and for improvement of symptoms.