Patterns of gene flow and gene introgression can be used to assess the risk of genetic pollution of wild for-est trees from widespread cultivated trees. A comprehensive understanding of the genetic relationships and levels of gene flow among wild and cultivated common walnut ( Juglans regia ) has become an urgent issue. Using twelve microsatel-lite markers, we investigated the genetic diversity and gene flow between cultivated and wild trees of J. regia in the Qin-ling Mountains, China. A high level of genetic variation was detected in both cultivated and wild trees. The mean number of alleles per locus was 17.5. Observed heterozygosity (H O ) and expected heterozygosity (H E ) were 0.777 and 0.800, respectively. Pollination of mother trees was not by nearest neighbors, and a paternity of 60.7％ of offspring evaluated could not be assigned to a local, sampled tree. Pollen flow from cultivated trees to wild trees was infrequent (5.4％), and selfing rates ranged from zero to 25.0％. Male parents were located from 0 to 1005 m from their female partners, with an average pollination distance of 285.1 m. These results are discussed in light of the cultivated species\' diversity, outlin-ing the frequent spontaneous genetic contributions from the wild to the cultivated compartment. In addition, the pol-len flow parameters provide useful information about the dynamics of pollen movement within J. regia populations.