We report two different cases of bacteremia caused by two recently described Selenomonas species, Selenomonas artemidis and Selenomonas infelix. Both species are normally found in human buccal flora. S. artemidis bacteremia appeared in a patient (number 1) who presented with an air-fluid pulmonary cavity and clinical conditions consistent with an anaerobic lung abscess. While the patient improved with antibiotic therapy, cultures of respiratory secretions yielded Mycobacterium tuberculosis. This case demonstrated a strong possibility of a coexisting lung abscess due to S. artemidis. S. infelix bacteremia appeared in a cancer patient (number 2) with heart disease during preterminal acute respiratory distress. It was more difficult in this case to assess the clinical impact of the Selenomonas organisms on the patient.