A model to describe hydrogen desorption from SiGe(100) that takes into account the nature of the surface bonding is presented. It is based on the presence of three dimer types in the SiGe(100) surface (Si-Si, Ge-Ge, and Si-Ge), in which there is a thermodynamic preference of hydrogen atoms to pair up before the desorption reaction. The desorption kinetics are, therefore, assumed to be controlled by the population of paired hydrogens in the three dimer types, according to a first-order law. It is also assumed that diffusion, which tends to drive the occupancy of hydrogen atoms in the dimers towards the thermodynamic equilibrium distribution, is not instantaneous. The comparison with experimental results shows that desorption is a diffusion limited process.