Abstract An improved strategy for the dideoxy chain termination sequencing of M13 recombinant DNA using enzymatically generated primers is presented. It involves synchronous extension of the universal primer with the Klenow fragment of DNA polymerase I at an average rate of 200 deoxynucleoside triphosphates per minute to the immediate downstream region of a preselected restriction enzyme site. Subsequent cleavage with the restriction enzyme generates the short primers with homogeneous 5′ ends which can be used for further sequencing. The next restriction sites are selected in the newly sequenced regions of DNA by means of a microcomputer. By repeating this primer extension-cleavage-sequencing strategy sequences altogether about 6 kb long from several recombinant single-stranded M13 DNAs have been determined by using twenty restriction enzymes with different specificities.