A micropipette aspiration technique was used to study the extent of adhesion of live and glutaraldehyde-fixed endothelial cells to four solid fibres with different surface tensions, γ SV: glass (γ SV > 72mj m −2); nylon (γ SV = 41 mJ m −2); polyester (γ SV = 30 mJ m −2); FC721-coated glass (γ SV = 13 mJ m −2). The cells and the fibres were immersed in phosphatebuffered saline (PBS), distilled water (for fixed cells), and complete culture medium. The contact angles of PBS on layers of cells were measured by the Axisymmetric Drop Shape Analysis-Contact Diameter (ADSA-CD) technique. Subsequently, the contact angle data were used in conjunction with the equation of state approach to determine the cell surface tensions, γ CV. For a live cell layer, the contact angle was 3.1 ° corresponding to a γ CV value of approximately 72 mJ m −2, and for fixed cells, an average contact angle of 36.6° was measured corresponding to a γ CV of approximately 60 mJ m −2. A small positive pressure of 1 Pa was applied to deposit the cells onto the fibres before the initiation of aspiration. The force of detachment is reported as a function of the duration of pressure application for the four test fibres in each medium. The results are interpreted by using a thermodynamic model for cell adhesion based on the relevant interfacial tensions. For both live and fixed cells, the forces of detachment increase with increasing duration of pressure application. The measured forces ranged from (3 ± 0) × 10 −11N (live cells in culture medium on glass) to (3709 ± 374) × 10 −11 N (fixed cells in PBS on FC721), where the errors are the 95% confidence limits. For fixed cells with PBS as a medium, the measured forces of detachment increased with decreasing solid surface tension. This corresponds to a trend predicted by the thermodynamic adhesion model for the case of surface tension of the liquid γ LV > γ CV and confirmed by the contact angle measurements. In water, although the magnitude of the forces is smaller than that in PBS, the trend is the same as that in PBS and is again predicted by the model. In complete culture medium, the extent of adhesion decreases greatly and the forces of detachment for all test surfaces are indistinguishable from one another. This can be attributed to the prior adsorption of proteins from the medium onto the fibres, resulting in an alteration of their surface properties. For live endothelial cells in PBS, the trend is opposite to that for the fixed cells. According to the thermodynamic model, this trend corresponds to the case of γ LV < γ CV. Finally, for live cells in complete culture medium, the forces of detachment increased with decreasing fibre surface tension. Since the protein molecules from the medium and the cells adsorb onto the fibres and the liquid-vapour interface, their surface tensions cannot be precisely determined. The thermodynamic model cannot be used to interpret the trend because of lack of knowledge about the surface energetics of this system. Overall, it is demonstrated that micropipette aspiration is a sensitive technique for characterizing the strength of cell adhesion to different solid substrates.