Ab initio averaged relativistic effective core potentials (AREP) and spin-orbit (SO) operators are reported for the elements Am through element 118. Two sets have been calculated for certain elements to provide AREPs with varying core/valence space definition, thereby permitting the treatment of core/valence correlation interactions. The AREPs and SO operators are tabulated as expansions in Gaussian-type functions (GTF). GTF valence basis sets are derived for the lowest energy state of each atom. The reliability of the AREPs and SO operators is gauged by comparing calculated atomic orbital eigenvalues and SO splitting energies with all-electron relativistic values.