We report a case of pathologically demonstrated chorioamnionitis due to Capnocytophaga species. The mother had high fever and marked uterine tenderness, and the infant had poor Apgar scores, fever, and pulmonary infiltrates. Both recovered after receiving specific antibiotics. Pathological examination of the placenta revealed acute chorioamnionitis, subchorionitis, and vasculitis of the umbilical vein. The dramatic clinical and pathological features of this case are compared with those of the nine previously reported cases of infection due to Capnocytophaga species occurring in pregnancy.