Random amplified polymorphic DNA (RAPD) markers were used to estimate the level and pattern of genetic diversity in Microtus fortis pelliceus populations from the mainland and islands of the Russian Far East. No markers were found both for individual populations and for the mainland or island voles as a whole. However, they appeared to be different in both their allele frequencies and microevolution mode based on correlation pleiad analysis. The island populations demonstrated a higher level of genetic differentiation among themselves than did mainland populations and each mainland population probably represents more genetic diversity than any population of islands. Overall, genetic variation between island and mainland M. f. pelliceus populations was low (Dst = 0.003), and can be explained by a low value of gene differentiation coefficient (Gst = 0.058). Nevertheless, exact test did not support the hypothesis that both united mainland and united island populations belong to the same genetic unit (p = 0.0025). RAPD data reliably distinguished voles of Matveeva Island, which are strongly differentiated by morphological traits, and this in turn did not exclude the island speciation event. Unlike UPGMA and NJ trees for individuals, population UPGMA strongly separated island voles from the mainland conspecifics, and MS reconctructions identified the Amur population as an ancestor.