Real-time PCR, namely the deltadeltaCt method was used to determine the relative copy number of Potato virus A (PVA) P3 gene in the genome of the T1 generation of 18 transgenic tobacco lines. These results were compared with segregation ratios of kanamycin (Km)-resistant phenotype in T1 plants of each line and were found to be, in general, concordant. All the five lines with the Mendelian segregation ratio of 3:1 carried one gene copy. In 12 of 13 lines with uneven segregation more inserted gene copies were detected. Only for one line the real-time PCR and phenotype segregation differed. According to our results the real-time PCR of T1 generation may be used as supplementary method of estimation of the number of transgene copies in the case of nonavailability of the original T0 plants.