Foreign bodies made of polymethylmethacrylate coverslips were implanted subcutaneously into guinea pigs, were explanted four weeks later, and were tested for in vitro adherence of Staphylococcus aureus strain Wood 46. In the presence of serum, the level of staphylococcal adherence to explanted coverslips was 20 times higher than that of adherence to unimplanted coverslips. Adherence to explanted coverslips was caused by fibronectin deposits on the foreign body surface and was inhibited in a dose-related fashion by specific antibodies to fibronectin.