To explore the efficacy of single dose ciprofloxacin therapy in cholera, a randomized, open, controlled clinical trial was carried out. Seventy-four adult patient with positive Vibrio cholerae 01 isolates were assigned to receive either ciprofloxacin in a single dose of 1 g (CIP1), or ciprofloxacin 500 mg b.i.d., for 1 day (CIP2), or doxycycline 100 mg b.i.d., for 3 days (D), or, for control, no antibiotics. Mean liquid stool output volume did not show any statistically significant difference among CIP1, CIP2 and doxycycline groups The mean duration of diarrhoea in CIP1 group, on the other hand, was significantly lower than that from the D group (p = 0.004), and the control group (p < 0.001). Bacteriologic clearance at the fourth day of treatment were 95.2% for CIP1, 89.5% for CIP2, 90.5% for D group and 15.4% for the control group. We conclude that a single 1 g ciprofloxacin dose is equivalent to doxycycline in its bacteriologic success but has advantages in shortening the duration of diarrhoea and simplicity of use as a single dose.