Reference is made to the results obtained in 24 children, from 11 months to 12 years, affected with acute pneumopathies and treated with fosfomycin with a dosage of 200 mg/kg/day. In all cases a clinical, radiological, biological and bacteriological study was carried out. At the same time, levels of fosfomycin in plasma and sputum were checked every 5 days during the course of treatment. In the 4 cases of pleurisy the level of antibiotic in the pleural liquid was also checked. The concentration of fosfomycin in the sputum gives very variable results with average values oscillating between 16.5 and 23.4% of the plasmatic level respectively at the beginning and end of treatment, a cumulative effect of the antibiotic being observed. Concentration in pleural liquid oscillates between 39 and 50%. The clinical, radiological and biological evolution has been favourable in 21 cases, unfavourable in two cases and in one case treatment had to be suspended because of the apparition of a cutaneous necrosis. Apart from this case no notable toxic effects were observed. Children do not support intramuscular injections very well and intravenous injections often cause phlebitis.