The goals of this study were to evaluate the in vitro antistaphylococcal activity of vascular Dacron prostheses to which a type I collagen and an antibiotic had been bonded. Collagen was fixed to the prosthesis either by an original grafting procedure or by impregnation. The antibiotics used included rifampin, vancomycin, and amikacin. They were bonded to the prosthesis either at the same time as the collagen or by soaking the prosthesis in an antibiotic solution at the beginning of the experiment. Each prosthesis was sliced into 6 mm diameter circles and preserved in a solution of saline and albumin, which was changed every day. Three disks were retrieved from each prosthesis at the beginning of the experiment and then every 24 hours; these were placed in gelose smeared with Staphylococcus aureus. The diameter of the inhibition area of each disk was measured at 24 hours. The initial inhibition area (So), the time at which the inhibition area was equal to 50% of So, and the time at which the activity was nil were used to characterize the activity of the prostheses and to calculate a beta coefficient of decreasing activity. The prostheses bonded with vancomycin or amikacin did not show adequate activity. Those bonded with rifampin were effective for at least 4 days. When rifampin was grafted to the prosthesis, the So was 278.6 mm2, 50% of So was reached within 10.4 days, the duration of effective activity was 25.7 days, and the beta coefficient was 0.067. The two prostheses soaked in rifampin had a significantly more rapid decrease (beta = 0.19 and 0.56) and a shorter duration of effective activity (12.4 and 4.5 days). Both collagen-coated prostheses, whether impregnated or soaked with rifampin, have a sufficient duration of activity to be tested in an animal model.