Polyamide-oligonucleotide derivatives of the formula F[(DNA-Li).sub.q(PNA-Li).sub.r(DNA-Li).sub.s(PNA).sub.t].sub.xF' wherein q, r, s, t are, independently of one another, zero or 1, where the total of two or more adjacent q, r, s and t.gtoreq.2; x is 1 to 20; DNA is a nucleic acid such as DNA or RNA or a known derivative thereof; Li is a covalent linkage between DNA and PNA, where the covalent linkage comprises a bond or an organic radical with at least one atom from the series consisting of C, N, O or S; PNA is a polyamide structure which contains at least one nucleotide base which is different from thymine; and F and F' are end groups and/or are linked together by a covalent bond, and the physiologically tolerated salts thereof, a process for their preparation and their use as pharmaceutical, as gene probe and as primer, are described.