Corona treatment of polystyrene (PS) and polyethylene resulted in an increase in the interfacial energy (gamma(sv)) of these surfaces, primarily due to an increase in the polar forces. The number of Vero cells which attached and the strength of attachment were higher on corona-treated surfaces, increasing as gamma(sv) increased. Inoculum concentration did not affect the percentage of cells that attached. Experiments were performed in Dulbecco’s modified Eagle’s medium containing 10% fetal bovine serum hence cellular attachment was most likely preceeded by adsorption of serum proteins. A minimum of 1 h of incubation under static conditions resulted in the maximum number of cells which attached and which remained attached after shear stress (33.0 dynes/cm(2) for 5 min) was applied. Experimental results with corona treated surfaces agree with the theoretical predictions for the free energy of adhesion of Vero cells in the medium used, indicating that interfacial energy plays an important role in attachment. The model predicted that substrates with a gamma(sv)>55.6 ergs/cm(2) (i.e. Theta(H2O)<39 degrees) would have a positive energy of adhesion. Such substrates did have >60% cell attachment. Since the model is valid if only van der Waals and Lewis acid-base interactions are dominant, these forces probably played a major role in the adsorption of serum proteins. Polylysine-treated PS and tissue culture PS did not follow the model. In the first of these two cases, electrostatic interactions probably played a more important role since the surface was covered with a positively charged protein.