Somaclonal variations of regenerants obtained in vitro by callus cultures possess a spectrum of genetic and epigenetic modifications (PJ Larkin, WR Scowcroft., 1981; Kaeppler SM, HF Kaeppler, Y. Rhee, 2000). The amplitude of such deviations in various species of plants is determined by genetic, physiological, chemical and physical factors. Thus, different genotypes, nutrient media, explants types, conditions and terms of subculture could be a source of generating somaclonal variations. In addition, in vitro cultivation for long time can reduce the ability of plant regeneration (Wang QM, Wang L., 2012). Experimental mutagenesis (chemical, physical, biological techniques) in complex with in vitro culture is used for expanding the spectrum of induced variability in different plant species. Their identification is a requirement no mater of the ultimate intention – to increase or stabilize deviations of initial forms. Today researchers use a large spectrum of methods to assess somaclonal variations by morphological, physiological, biochemical, cytogenetic and molecular markers (RAPD, AFLP, RFLP, ISSR, SSR). Polymorphism of potato tuber protein is a basic tool used in study of variability in potato varieties (J. Barta, Courts V., J. Divis, 2003).  The aim of the present study is to evaluate somaclonal variation accompanied by virus infection in potato based on electrophoretic studies.  As biological material, were used potato regenerants (Ostara and Impala varieties) obtained in vitro by callus cultures from leaf fragments of virus infected  (Potato virus M and Potato virus Y) and control plants (virus free). The electrophoretic analysis was performed for storage proteins and peroxidase in potato tubers from above mentioned variants. The extraction was carried out in solution of 0.01M Tris -glycine with addition of 0.5% sodium ascorbate. Electrophoresis was performed in 10 % polyacrylamide vertical gels after BJ Davis (1964). For protein polymorphism evaluation, the gels, after fixing in mix of trichloracetic acid - alcohol - distilled water (10:25:65), were stained in Coomassie blue R – 250. For peroxidase estimation, the gels were stained in R benzidine (0.2%) and hydrogen peroxide (10%).  It was established that some potato somaclones regenerated from explants of both experimental and control variants differed from original forms after the protein components and peroxidase isoforms. As a result of electrophoretic analysis of proteinograms in potato tubers of somaclones, an increased polymorphism for Ostara variety and less pronounced in the Impala variety was attested. Differences were found between the number of bands and their intensity and location.  So, from the total 23 protein bands attested in analyzed somaclones a greater diversity was established for components with a relatively lower (Rf 0.039 to 0.200) and increased electrophoretic mobility (Rf 0.428 to 0.830). Common for the most forms have been found the components with mobility between Rf 0.328 and 0.500. The study of peroxidase activity shows that the rate of common components for most forms was higher than for the proteins. A higher variability was recorded for Rf 0.133 to 0.168 and 0.415 to 0.435 components.  The results of electrophoretic analysis attest that the variability between somaclones and original forms is large and it is determined by genotype, presence of viruses in tissue of explants of donor plant. The biochemical deviation was confirmed by the variability of morphological characters.