cDNA was synthesized and cloned on the template of the genomic RNA of Marburg virus (strain Popp). Recombinant plasmids with specific cDNA inserts were selected and sequenced. The length of the open reading frame encoding the GP-protein is 681 amino acids. GP-protein is proposed to be an integral membrane protein. Computer-assisted comparison of the deduced amino acid sequence with those of different viruses revealed significant homology with the GP-protein of Ebola virus and with the 'immunosuppressive domain' of the P15E envelope proteins of some oncogenic retroviruses.