Thirty-two patients with severe biliary tract infections (cholecystitis and cholangitis) were treated with ciprofloxacin intravenously followed by oral ciprofloxacin. Complete clinical and bacteriological cure has been observed in 28 out of 32 patients and therapy failure occurred in four patients. Overall, no major adverse effects were encountered. These data suggest that intravenous ciprofloxacin followed by oral administration is an effective and safe agent for the therapy of severe biliary tract infections.