A rapid and efficient gene-cloning method was developed using oligodeoxyribonucleotide probes (approx. 30-mer) immobilized by their 5' terminal to the gel (LiChrosphare Si1000; used for high-performance liquid chromatography). The method allowed us to concentrate DNA fragments having a particular base sequence in an eppendorf tube with very high efficiency within 2 h. For example, genomic DNA encoding the human fibronectin gene (fn) was concentrated by this method and cloned into lambda Charon4A vector. Screening of the concentrated genomic DNA library for the 5' region of the human fn gene showed that approx. 30% of 3000 recombinant phages tested were positive clones. Various factors affecting cloning efficiency were investigated.