An ab initio model potential (AIMP) has been developed for the lanthanide series from Ce to Lu. The corresponding (14s10p9d8f) valence basis sets were optimized by means of the minimization of the valence SCF total energies. The relativistic effect was considered with the scalar relativistic third-order Douglas-Kroll approximation. The applicability of the present AIMP, and the valence basis sets, was tested for the lanthanide atoms, and a monoxide, CeO. Both the atomic and molecular AIMP calculations showed excellent agreement with all-electron calculations. The present AIMP scheme has proved to work well in the calculations of whole series of the lanthanides. (C) 2002 Published by Elsevier Science B.V.