Arcobacter were originally isolated from bovine and porcine fetuses by W. A. Ellis and colleagues in the 1970s. Arcobacter cryaerophilus, A. butzleri, and A. skirrowii have been recovered from animals with diarrhea and from livestock abortions. Arcobacter are recovered from abortions and enteritis in livestock, whereas human infections are mainly associated with enteritis. Arcobacter have been studied extensively in porcine abortions. Based on reports of recovery from animals with reproductive problems, results of serosurveys, and on limited experimental infections, the conclusion has been made that Arcobacter are pathogenic to livestock. Recovery of Arcobacter in the feces of livestock with enteritis suggests contamination of the premises and infection, perhaps via the oral route and hematogenous dissemination in the susceptible animal. The growing interest in Arcobacter will add impetus to establishing its significance to veterinary and human medicine.