Serotype 012 represented 15% of 244 isolates of Pseudomonas aeruginosa isolated in the hospital over a 2 year-period and most isolates of this serotype were resistant to multiple antibiotics. Combination experiments showed that fosfomycin and amikacin together were active against 92% of 012 isolates. It is recommended that serotyping be used systematically to identify 012 strains rapidly and fosfomycin/amikacin be considered as a presumptive antipseudomonal therapy in 012 infections.