Sixty-seven serum samples and 43 pathological material samples from wild boars, taken in 5 regions of Russia and in the Kharkov Region of the Ukraine in 2002 to 2005 were studied. Wild boars in some regions of Russia were shown to be carriers of Aujeszky's disease virus, porcine parvovirus, porcine circovirus type 2, lymphotropic herpesvirus-1, porcine cytomegalovirus, Mycoplasma hyopneumoniae and Pasteurella multocida. The classical swine fever (CSF) virus genome was detected by polymerase chain reaction in the samples from 10 wild boars from 2 Russian regions (the Tver and Moscow Regions). Sequencing of the E2 gene 5'-terminal region of detected CSF virus isolates showed that they were closely related to two field virus isolates early found in domestic pigs in the Moscow and Vladimir Regions, which suggests that there is an epizootic relation between the SCF outbreaks among wild boars and domestic pigs in these regions. Tests for porcine reproductive and respiratory syndrome, transmissible porcine gastroenteritis, porcine influenza, enteroviruses, and actinobacillus-induced pleuropneumonia were negative in all the regions under study.