The Minimal Inhibitory Concentrations of cefoxitin, clindamycin, metronidazole, and penicillin G against species of the Bacteriodes fragilis group from human origin was determined, by using an agar dilution method. The percentages of resistant tested strains of the B. fragilis group were 77% to cefoxitin, 31% to clindamycin, and 89% to penicillin G. No resistant strain for metronidazole was found at the breakpoint (16-mu-g/ml).