Fosfomycin, an antibiotic discovered in Spain, has a unique chemical structure and pharmacologic features that are promising for clinical therapy. It is only partially absorbed orally, with relatively low blood levels. Intramuscularly, however, absorption is complete with peak blood levels 3-5 times as high as orally, and rapid intravenous injections give serum concentrations almost twice as high as intramuscularly. Some accumulation occurs with all three routes, and concentrations in excess of 1,000 mug/ml are consistently obtained in the urine with parenteral doses every 6 h. The serum half-life is 1.5-2 h, urinary excretion is by glomerular filtration, the antibiotic is not bound to serum proteins, and the volume of distribution is large. Diffusion into tissues and body fluids is good. Thus, the pharmacologic characteristics of fosfomycin along with its low toxicity make it comparable in these respects to other well-established antibiotics.