Agar dilution anaerobic susceptibility studies using rifampin, vancomycin, metronidazole, and bacitracin individually and in combination were performed with Clostridium difficile. Fifty-five strains of C. difficile were studied. Eighty-five percent of strains tested (29 of 34) were synergistically inhibited by the combination of bacitracin and rifampin (fractional inhibitory concentration, less than or equal to 0.50).