Seventy-four cefoxitin-resistant Bacteroides fragilis group isolates were tested by the serial twofold agar dilution method for susceptibility to imipenem and other agents in medium with and without 5% sheep blood. Imipenem (MIC for 90% of strains tested, 1 microgram/ml) and metronidazole (MIC for 90% of strains tested, 2 micrograms/ml) were the two most active agents. The addition of 5% sheep blood to the medium had little or no effect on the activity of the antibiotics tested.