A diabetic patient with peripheral neuropathy and a foot ulcer developed osteomyelitis of the foot. Antibiotic therapy of the aerobes isolated from the ulcer resulted in no clinical improvement. Intravenous clindamycin therapy of the anaerobe isolated (Bacteroides fragilis) was associated with an incomplete and temporary response, but there was a dramatic response to oral metronidazole with healing of the ulcer and osteomyelitis. One year later there were no signs of recurrence.