In order to determine the liquor concentration of fosfomycin, we chose 27 patients who were suffering from meningitis with different etiology. According to route, type of administration and doses employed, we classified the patients into five groups. Blood samples were taken from the patients 1 h after concluding the administration of the antibiotic and 2 h after the CSF sample. The concentration of fosfomycin in the serum and the CSF were then determined in the laboratory. In order to evaluate the results we divided our cases into three groups according to the state of their meningeal inflammation. In the first group of patients with active meningitis, we obtained an average concentration of fosfomycin in the serum of 65.20 μg/ml and in the CSF of 10.88 μg/ml. In the second group of patients with meningitis in the remission stage, the concentration of fosfomycin in the serum was 83.58 μg/ml and in the CSF it was 9.63 μg/ml. In the third group of patients with their meningitis cured, the concentration of fosfomycin in the serum was 66.45 μg/ml and in the CSF it was 4.95 μg/ml. On the basis of the concentrations obtained and with regard to the sensitivity in vitro, we concluded that fosfomycin can be useful in the treatment of meningitis caused by Pneumococcus,Staphylococcus,E. coli and other gram-negative ba