Background. The reproductive incompatibility of cultivated (Pisum sativum) and wild (P. fulvum) pea species determines the difficulties of obtaining hybrids as well as the transfer of valuable wild parent alleles into interspecific hybrids and their use in the breeding process. The aim of the research was a comparative study of protein spectra of pea interspecific hybrids BC2F5 P. sativum × P. fulvum obtained by the authors and their parents. Materials and methods. The band composition of seed proteins in the interspecific hybrids of peas BC2F5, variety Stabil (P. sativum) × accession from VIR collection I-609881 (P. fulvum) has been studied. Effectiveness of parent gene transfer determining each polymorphic position of electrophoretic spectrum were evaluated. Results. The ratio of the actual frequencies of the bands of the cultivated and wild parents in the introgression lines corresponded to the expected level in 73% positions of the electrophoretic spectrum. The introgression rate of individual seed protei