A fraction (P1) which showed DNA polymerase III holoenzyme activity was obtained by partial purification including Polymin P fractionation from extracts of E. coli K-12 wild type (pol A+, pol B+) cells. The P1 fraction was composed of three macromolecular complexes, 11 S, 18 S and 24 S, all of which possessed holoenzyme activity. The activity of the P1 fraction was maximal at about 70 mM NaCl. The synthesis of long-chain poly(dT) with a poly(dA) oligo(dT)10 primer was dependent on the presence of ATP, but not on the presence of spermidine, suggesting that the single-stranded DNA binding protein (SSB) was present in the fraction. The intermediate lengths of the products in the absence of ATP and NaCl also suggest the functioning of DNA polymerase III'.