Genetic heterogeneity and evolutionary relationships among selected strains of adenovirus type 7 (Ad7) isolated in the former USSR were examined using the restriction endonuclease Cfr131 with a 4-base recognition cleavage site. The population of adenovirus type 7 showed less expressed genome polymorphism and significant structural distinctions as compared with that of adenovirus type 3. The Ad7 evolution in the USSR (1976-1988) independent on that demonstrated in other countries is discussed.