Of the approximately 2,500 California bighorn sheep (Ovis canadensis californiana) in Oregon, USA, the majority descend from a single transplant of 20 animals from British Columbia, Canada, in 1954. Recently, several populations have experienced poor recruitment, raising concerns that populations may be experiencing inbreeding depression resulting from a genetic bottleneck. We sampled 117 animals from 5 populations in Oregon and 1 population in Nevada to determine genetic variability within and among populations. We found that Oregon populations had fewer mean alleles per locus (2.2–2.4), lower heterozygosity (0.28–0.36), and higher inbreeding potential than animals from Nevada (3.8 alleles/locus, H = 0.53). These results now provide the baseline for rigorous ongoing evaluation of changes to allelic variability, inbreeding potential, variation among populations, and their effects on population demographics for Oregon's California bighorn sheep program. We suggest that evaluation of genetic variability in other source and recipient populations should be used to further understand how and when genetic management can be used for bighorn sheep conservation and management.