The brief exposure of bacteria to high antibiotic concentrations can result in prolonged suppression of bacterial growth termed postantibiotic effect (PAE). A pathogenic Staphylococcus epidermidis strain (RP-62) was exposed to 2X and 6X minimum inhibitory concentrations (MIC) of cefazolin, vancomycin, or rifampin for 1 hr and incubated for 2 to 24 hr in inhibitory-free broth. PAE was defined as the difference in time required for a 1.0 log increase in test (T) vs control (C) cultures (PAE = T-C). PAE was observed only for rifampin: 6 hr at 2X MIC and 8 hr at 6X MIC. Bacterial adherence to Dacron grafts was calculated in PAE vs control cultures by a quantitative culture technique for graft specimens incubated 2 to 24 hr. A demonstrable PAE and its impact on adherence were found to be both antimicrobial and concentration dependent. A significant decrease in staphylococcal adherence to velour-knitted Dacron was demonstrated by rifampin at 2X MIC (P less than 0.05) and 6X MIC (P less than 0.01). This phenomena may be useful in reducing bacterial adherence and colonization of bioprosthetics in the perioperative period. Preoperative suppression of staphylococcal skin flora by high dose antimicrobials can alter the capacity of these organisms to adhere to vascular prosthetic grafts and, if incorporated into antibiotic prophylaxis regimens, may reduce graft colonization.