Sensitivity to fosfomycin has been studied and recorded throughout a period of 12 months in the bacteriological isolations originating from this Intensive Care Unit. The 548 samples were biological products obtained from patients admitted to this unit (bronchial exudates, urine, wounds, blood, cava catheters and cere-brospinal fluid). The highest percentage of sensitivity was given by S. aureus coagulase (+), S. fecalis and E. coli (91, 89 and 84% respectively), and the least by P. aeruginosa and Providencia (33 and 8% respectively). A summary is included of 8 seriously ill patients admitted with varied septic processes, produced by germs sensitive to fosfomycin and treated with this, in 5 cases alone and in 3 cases with gentamicin and carbenicillin. Of those who were treated with fosfomycin alone: three were cured, one died on the sixth day through circulatory, respiratory and renal deficiencies and the other with respiratory deficiency. Those treated with the combined antibiotics: two were cured and the other died of sepsis on the fourth day.