The invention relates to retroviral expression vectors with cell-specifically modulatable promotors. The vectors can be used, for example, for the cell-specific expression of therapeutically valuable genes in gene therapy. The invention specifically relates to retroviral expression vectors containing at least the following elements, in a functional configuration: a) DNA sequences for the packaging of the vector RNA and for the cell-specific expression of proteins or peptides which are coded by heterologous DNA nucleotide sequences; b) one or more DNA nucleotide sequences coding for a protein or a peptide and characterized in that for cell-specific expression said DNA sequences contain a cell-specifically modulatable promotor region of a human endogenous retroviral DNA nucleotide sequence (HERV).