Our EPR measurements of dislocation spectra in silicon are reviewed with special emphasize on the possible atomic models of these centres. New information upon the atomic arrangement around the single electron centre Si-Kl can be deduced from recent measurements of hyperfine lines belonging to this centre. From these results is concluded that the partial dislocations of split screw dislocations are the most probable location of the dislocation centres. In addition the effect of illumination on these centres is discussed : band gap light as well as light with 0.68 eV photon energy enhances the number of coupled spin centres and decreases the Si-Kl spectrum