DNA polymerase found in an extract from eggs of the teleost fish Misgurnus fossilis (loach) has been identified as an enzyme of the delta type. The enzyme was purified 4000- to 5000-fold from the extract by liquid chromatography. The DNA polymerase activity was sensitive to the inhibiting action of aphidicolin but resistant to N2-(p-n-butylphenyl)-2'-deoxyguanosine 5'-triphosphate (BuPdGTP). The enzyme activity correlates with the presence of a polypeptide with molecular mass of 120-130 kD that interacts specifically with polyclonal antibodies against calf thymus DNA polymerase delta as revealed by Western blotting and is presumably the catalytic subunit of the enzyme. The loach DNA polymerase possesses the 3'-->5'-exonuclease activity specific to single-stranded DNA and catalyzes distributive elongation of primers in primer-template complexes.