Abstract: The invention relates to a device for the automatic determination of nucleic acid sequences. The sequencing reaction occurs by the parallel sequential construction of the strands complementary to individually-fixed single-strand nucleic acid chains. The automatic sequencing carries out said sequential construction and detects electromagnetic radiation from individual marked nucleotides (NT*s) incorporated in the complementary strands. The sequence of the immobilised nucleic acid chain is determined from the order of the incorporated NT*s.