1-2 g/day or 3-4 g/day phosphomycin were administered per os to children and adults respectively for an average of 5.2 days in the outpatient treatment of 28 males and 18 females with parodontitis, gingivitis and dysodontiasis of bacterial origin. All patients presented swelling of the soft parts and 34 (74%) had hyperpyrexia. A clinical cure was obtained after 9 days in all cases. Fever lasted an average of 2.4 days and disappeared after 6 days. Swelling lasted an average of 3.6 days and disappeared after 8 days. Tolerance was excellent. Two patients (4.3%) displayed diarrhoea and nausea and one (2.2%) pruritus. These side-effects did not necessitate the suspension of treatment. It is felt that phosphomycin may be regarded as a drug of choice in the treatment of odontostomatological infection of bacterial origin.