Available information about the safety of intravenous (i.v.) administration of ciprofloxacin is reviewed. No increased incidence of systemic toxicity is apparent over the oral route. CNS side effects occur, but at a low rate and they are mild. Caution is indicated in patients with tendency for seizures. Laboratory changes are minimal, mainly mild elevations of liver enzymes. No increased risk of crystalluria has been seen. Local side effects in the form of erythema and burning are relatively common in some volunteer studies and are also seen in clinical studies, infusion phlebitis also occurs. It is recommended that i.v. ciprofloxacin is administered in slow infusion through a large or preferably central vein.