The electron.. electron interactions and the creation energy of a soliton in highly conducting polymers were calculated by using a correlated--basis-function method with a general screening Coulomb potential within the Kronig. Penny. model framework. Our results showed that even when the electron-electron interactions are considered，solitons are still the main charge carriers. The strong long-range electron-electron interaction is seen to reduce the creation energy of a soliton. A comparison with results based on the Hubbard model has been made. The 1imitations of the Hubbard model in this application were discussed.