Ciprofloxacin (120 mg/kg of body weight per day), chloramphenicol (300 mg/kg per day), and gentamicin (30 mg/kg per day) were compared with placebo in a BALB/cj mouse model of scrub typhus. All animals treated with ciprofloxacin and chloramphenicol survived. All animals treated with gentamicin or placebo died. All surviving animals showed evidence of seroconversion. Ciprofloxacin and chloramphenicol were statistically more effective in preventing death than gentamicin or placebo.