Some peculiar results of deep-level transient spectroscopy (DLTS) measurements on plastically deformed hydrogenated Si are explained in terms of a model for the driven reconstruction of dislocations. Driven reconstruction may be responsible for the reduction in the density of high-temperature electron paramagnetic resonance (EPR) centres after predeformation and after deformation during heat treatment in a hydrogen atmosphere. The model for driven reconstruction is based on the assumption that the non-reconstructed state is the lowest energy state of the dislocation core. Together with numerous results concerning electrical conduction along dislocation cores, the considerations presented in this Letter strongly indicate that dangling bonds exist within dislocation cores in Si. The absence of a dislocation-related EPR signal suggests that there must be a reason, intrinsic to the dislocation core, by which dangling bonds in dislocations do not carry unpaired electrons.