A review is given of current antibiotic treatment of anaerobic infections. It is emphasized that infections with Bacteroides fragilis constitute the main problem, virtually all other anaerobe organisms of clinical significance are sensitive to penicillin. Particularly useful antibiotics for infections with B. fragilis are cefoxitin, chloramphenicol, clindamycin and the nitroimidazoles. Vancomycin is the drug of choice for pseudomembranous colitis provoked by Clostridium difficile.