Abstract: A method for determining the nucleotide sequence of a chromosome. The chromosome is hydrolyzed to form a mixture of oligonucleotides having unknown nucleotide sequences. The mixture is exposed to a library of oligonucleotide probe pairs having known sequences. The probe pairs are located so that they hybridize to outer opposed sections of the chromosomal oligonucleotides. The use of oligonucleotide probe pairs provides for sequencing of relatively long unknown DNA sequences using relatively short oligonucleotide probes.