The structural relaxation kinetics at the glass transition in tellurium oxide (TeO2)-based glasses has been examined from viscosity and beat-capacity measurements to clarify the features of the structural relaxation in fragile oxide glass-forming liquids. A large decoupling between enthalpy relaxation and viscous flow, i.e., a large discrepancy between the activation energies for the enthalpy relaxation (recovery), DeltaH, and viscous flow, E-eta, has been demonstrated in TeO2-based glasses. The values in xK(2)O.xMgO.(100 - 2x)TeO2, glasses, for example, are similar to919-1051 kJ/mol for DeltaH and similar to 577-701 kJ/mol for E,,, given the ratio of DeltaH/E-eta, approximate to 1.44-1.59. Some viscosity and heat-capacity data (all data have been reported previously) obtained from similar experiments in Sb2O3-B2O3 glasses belonging to the category of strong glass-forming liquids have been reanalyzed in this paper for comparison; a strong coupling was found to exist between DeltaH and E-eta, i.e., DeltaH/E-eta approximate to 0.98-1.18. An origin of decoupling between DeltaH and E-eta in fragile glass-forming systems such as TeO2-based glasses has been discussed by considering the glass structure model for fragile glasses; strongly bonded correlated (highly constrained) regions are surrounded or connected by weakly bonded noncorrelated (unconstrained) parts.