A microorganism isolated from an aborted sow's placenta has been proposed as a novel species, Arcanobacterium abortisuis. The lesions in the placenta were suppurative and necrotic placentitis, whereas lesions of three fetuses were suppurative bronchopneumonia. Gram and Grocott-positive organisms in these lesions were immunolabeled with anti- Arcanobacterium abortisuis antibody. This is the first case report, which showed the association of Arcanobacterium abortisuis with the aborted lesions of a pig.