Anaerobic and aerobic cultures of facial and mandibular abscesses were made from 12 blue duiker (Cephalophus monticola fusicolor) housed at the Deer and Duiker Research Facility of the Pennsylvania State University (USA). Increases in concentrations of total protein and serum globulin occurred in all cases. Actinomyces pyogenes was isolated from nine animals. Fusobacterium necrophorum was present in eight and Bacteroides sp. was found in seven animals; other genera of isolated bacteria included: Streptococcus (from two animals), Lactobacillus (one), Staphylococcus (one) and Actinomyces (two). Eight (67%) of affected animals were ≤2 yr of age. Facial soft tissues and mandibles were the tissues most often affected. Tissues within the oral cavity were not affected at the time of presentation. A common finding, not reported in other host species with necrobacillosis, was the presence of nondestructive mandibular proliferation.