The nucleotide sequence of the intercistronic region between genes F and G in bacteriophage X174 DNA has been determined. This has been achieved by DNA sequencing techniques which rely on primed synthesis. The intercistronic space, which is precisely defined at both ends by protein sequence, is 111 nucleotides long and contains 12 terminator codons covering all possible phases. A region of hyphenated 2-fold symmetry is observed, in which 28 out of 36 nucleotides form a symmetrical array in the double-stranded DNA. This region is identified as containing the major hairpin loop found in X174 single-stranded viral DNA. Possible functions for this part of the X174 genome are discussed.