Adhesion of poly(dimethylsiloxane) cross-linked networks to silicon oxide surfaces was studied using the Johnson-Kendall-Roberts method of contact mechanics. An increase in adhesion hysteresis was observed in the order of increasing molecular weight between cross-links. The log/log plots of energy release rates, G, vs molecular weights (M-n), for different crack propagation rates (-da/dt), gave a family of straight lines, with their slopes increasing with increasing -da/dt. When a plot of the slopes vs crack propagation rates was extrapolated to -da/dt = 0, it was found that the slope at zero velocity is equal to 0.47, in agreement with the 1/2 power predicted by de Gennes (C. R. Acad. Sci. Paris 1995, 320, 193). On the other hand, when the network was kept for 30 min at maximum load before unloading, the scaling factor was 1/3. This decrease in scaling factor is attributed to the molecular weight dependence of network relaxation rates. The results suggest that the polymer chain in a network, when in contact with a surface under conditions close to equilibrium, behaves like a chain in a polymer melt near a surface.