A natural focus of hantavirus infection was detected and examined during the studies conducted in 2000-2002 around the Sochi (the western spurs of the Great Caucasus Ridge, which descended to the Black Sea (the Krasnodar Territory of Russia). At least 4 rodent species, such as Microtus majori, A. (S.) ponticus, A. agrarius, A. (S.) ciscaucasicus, were shown to participate in the circulation of hantaviruses. A comparative analysis of the nucleotide sequences of genomic S- and M-segments of hantaviruses has provided evidence that 13 viral RNA isolates from the A. (S.) ciscaucasicus belong to the Dobrava/Belgrade virus clade; however the RNA isolate from the Microtus majori belong to the Tula virus clade.