Atomic Force Microscopy (AFM) was used to measure the surface elastic modulus of cross-linked poly(dimethylsiloxane) (PDMS) by measuring the interaction between the AFM tip and the sample surface. PDMS was synthesized by reacting vinyl end capped oligomeric dimethyl siloxane with methyl hydrosiloxane cross-linker using a platinum complex catalyst. Different weight proportions of the oligomeric precursor and the cross-linker (40:1, 30:1, 20:1, and 10:1) were cured at 65 „aC for four hours to give four PDMS samples of varying cross-linking levels. The cross-linking density of the polymeric samples was determined using swelling experiments in toluene, and the degree of polymerization (DP) between cross-links was found to be 13, 38, 112, and 321, with higher values representing lower percent cross-linking. Samples for AFM studies were cast on a single NaCl crystals, and silicon cantilevers were used with spring constant of ~3 N/m. Plots of the cantilever deflections versus tip distance were obtained from AFM analysis at a tip-sample approach rate of 50 nm/s. The cantilever deflections were reported in terms of force on the cantilever, and the corresponding force versus indentation plots were analyzed using Matlab. The elastic modulus values were calculated from the indentation plot data using the "two-points method" approach reported by Sun and Walker1, where the hyperboloid shape of the cantilever tip was used to determine the surface contact area. Elastic modulus values of 7.5 MPa, 2.4 MPa and 1.5 MPa were obtained for PDMS samples corresponding to DP of 38, 112 and 321, respectively.