The in vitro activity of ciprofloxacin, erythromycin, telithromycin, teicoplanin, linezolid and quinupristin-dalfopristin was tested against human derived pathogenic corynebacteria. The MICs of these antibiotics were measured using the agar dilution method against 31 strains of Corynebacterium jeikeium, 58 Corynebacterium amycolatum (including 33 multidrug-resistant strains) and 64 Corynebacterium urealyticum clinical strains. A high resistance rate to ciprofloxacin and erythromycin was found in the three species. Telithromycin was much more active than erythromycin (MIC(90) of erythromycin >or=128 mg/l for all three species; MIC(90) of telithromycin: 4 mg/l for C. jeikeium, 64 mg/l for C. amycolatum and 1 mg/l for C. urealyticum). There were no teicoplanin-resistant (MIC(90) 1, 0.5 and 1 mg/l, respectively) or linezolid-resistant strains (MIC(90) 1, 0.2 and 0.5 mg/l, respectively). Quinupristin-dalfopristin was active against most strains with an activity similar to linezolid, but three C. jeikeium and one C. amycolatum showed MICs >or=4 mg/l. Telithromycin showed much better activity against corynebacteria than older macrolides. Synercid and linezolid were active against most isolates tested, including multidrug resistant strains.