The combined activity of fosfomycin with rifampin, pefloxacin and imipenem was investigated, by the checkerboard method performed in liquid medium, against 50 clinical isolates of staphylococci (25 Staphylococcus aureus and 25 coagulase-negative staphylococci). The combination of fosfomycin plus rifampin had an additive bacteriostatic effect and an antagonistic bactericidal effect. Fosfomycin combined with pefloxacin was found to be additive or moderately synergistic. Fosfomycin in combination with imipenem was generally highly synergistic, especially against meticillin-resistant strains; however the bactericidal effect was occasionally antagonistic.