Bactericidal effects of quinupristin/dalfopristin and ciprofloxacin have been studied against six strains of Staphylococcus epidermidis, with varying erythromycin resistance phenotypes and varying abilities to form slime and adhere, growing as biofilms. Ciprofloxacin and quinupristin/dalfopristin killed (2-3 log10 cfu/mL) planktonic and sessile cells slowly, but progressively, over the course of 48 h. Rates of killing by quinupristin/dalfopristin were independent of concentration over the range 5-30 mg/L, and were somewhat slower than those seen with ciprofloxacin. These findings suggest that quinupristin/dalfopristin may be useful in the treatment of line-associated infections.