Mice infected with Brucella melitensis were treated with streptomycin, co-trimoxazole, ciprofloxacin, doxycycline, and rifampin intraperitoneally and with ciprofloxacin, ofloxacin, pefloxacin, doxycycline, and rifampin orally for 14 to 21 days. Doxycycline- and rifampin-treated animals (either route) demonstrated a cure rate significantly better than that of controls. Longer therapy periods were associated with a significantly better outcome. Therapy failure was observed in all mice treated with ciprofloxacin, ofloxacin, and pefloxacin administered orally as well as in mice treated intraperitoneally with ciprofloxacin. Our findings demonstrate that treatment of experimental brucellosis in mice with doxycycline and rifampin yields therapeutic results that are superior to those yielded by treatment with quinolones.