The measurement of cell adhesion using single cell force spectroscopy methods was compared with earlier methods for measuring cell adhesion. This comparison provided a means and rationale for separating components of the measurement retract curve that were due to interactions between the substrate and the glycocalyx, and interactions that were due to cell surface integrins binding to a substrate-bound ligand. The glycocalyx adhesion was characterized by multiple jumps with dispersed jump sizes that extended from 5 to 30 microm from the origin. The integrin mediated adhesion was represented by the F(max) (maximum detachment force), was generally within the first 5 microm and commonly detached with a single rupture cascade. The integrin peak (F(max)) increases with time and the rate of increase shows large cell to cell variability with a peak approximately 50 nN s(-1) and an average rate of increase of 75 pN s(-1). This is a measure of the rate of increase in the number of adhesive integrin-ligand bonds/cell as a function of contact time.