Iron is one of the essential element for bacterial growth. To study the effect of chelation of iron on bacterial growth, 17 different strains of bacteria were cultured in chocolate-agar medium in the presence or absence of deferoxamine methylate (DM), a potent chelating agent for iron. A fairly low concentration of DM (10 mg/ml) in the culture medium markedly inhibited the growth rates of the three bacterial strains, B. catarrhalis, N. meningiditis and N. gonorrhoeae. In vivo effect of DM was also tested in mice that were intraperitoneally inoculated with a lethal number of N. meningiditis (2 x 10(8)/animal). After 40 h of inoculation, more than 90% of the control animals died for acute peritonitis. In contrast, animals which were intraperitoneally administered with DM showed a marked resistance to the inoculated bacteria without showing toxic effects of the agent: less than 30% of animals died of acute peritonitis caused by infection within 40 h. The results suggest that, in addition to the currently used antibiotics. DM might also be an useful therapeutic agent for treatment of bacterial infection.