Ferret kits inoculated intravenously (IV) withCampylobacter jejuni after pretreatment with parenteral iron developed more severe systemic signs and more prolonged bacteremia than untreated inoculated controls. Watery diarrhea began in both groups 2–16 h after inoculation and lasted less than 48 h.C. jejuni was cultured from rectal swabs 2–8 h after inoculation, and gut colonization persisted up to 15 days, suggesting that colonization does not necessarily induce diarrhea. Gut colonization occurred as rapidly after IV inoculation of ferrets in which the common bile duct had been ligated as it did in unligated controls.C. jejuni apparently reached the intestinal lumen by mucosal invasion from the bloodstream. Bacteremia following natural infection could thus result in repeated passages ofC. jejuni across the gut wall, exposing the mucosa to both the bacterial cells and their metabolic products. Histological evidence of an inflammatory response in the mucosa, without severe epithelial damage, suggests a toxin-mediated secretory diarrhea.