This paper presents data for threading dislocation velocities measured in Si-Ge heteroepitaxial thin films during in situ HVTEM annealing experiments. These data are compared to three models which were previously developed to describe the kink mode of dislocation motion. Two of these models, Hirth and Lothe  and Seeger-Schiller , are based on the discrete narrow kink representation. The other, developed by Büttiker and Landauer , is based on the macroscopic bulge model representation of the dislocation line. It is found that both the narrow kink models underestimate dislocation velocities in the stress range of the experiments and that a good representation of the data can be obtained by using the macroscopic bulge model in the dislocation length-dependent regime.