Two cases of mediastinitis and bacteremia caused byBacteroidesspecies following median sternotomy are described. In both patients, purulent sternal drainage and signs of systemic toxicity led to the diagnosis. Surgical reexploration and administration of appropriate antibiotics effected clinical cure. Although there is only a single previous case of anaerobic mediastinitis following median sternotomy incision reported, these two cases suggest that this unusual infection may not be so rare as previously thought.