The adherence of staphylococci to monolayers of human mesothelial cells was studied. Adherence of Staphylococcus aureus to mesothelial cell monolayers was 3.4-fold better than to plastic (P less than .01) whereas that of Staphylococcus epidermidis was 3.0-fold less than to plastic (P less than .01). Neither serum albumin nor gelatin inhibited staphylococcal binding. S. aureus adherence correlated with the amount of cell wall protein A (r = .63, P less than .05) but not with fibronectin binding; it was significantly inhibited by the addition of purified cell wall lipoteichoic acid (55% +/- 2.7%), teichoic acid (34.5% +/- 3.4%), and protein A (25.6% +/- 2.9%) but not peptidoglycan. Protein A- and teichoic acid-deficient mutants adhered less well than their parent strains, and encapsulated S. epidermidis adhere well to human monothelial cells. Staphylococcal binding may involve cell wall lipoteichoic acid, teichoic acid, and protein A.