The susceptibility of 102 bacterial strains isolated from oral infections to ciprofloxacin, penicillin V, tetracycline and metronidazole was assessed by an agar dilution technique. Penicillin V was the most effective of the antimicrobials, with only three isolates resistant, while widespread resistance to tetracycline was seen. Metronidazole, as expected, was extremely effective against anaerobic isolates. Ciprofloxacin exhibited intermediate activity with the majority of MICs in the range of 1-4 mg/l. However, resistance was seen, particularly among Actinomyces and Wolinella species. In was concluded that, on the basis of these results, ciprofloxacin has limited potential for the treatment of oral infection but its potential for use in prophylaxis in head and neck surgery remains to be determined.