The predominant DNA polymerase activity has been isolated from the parasitic flagellated protozoan, Trypanosoma brucei. Like mammalian DNA polymerase-alpha the trypanosome DNA polymerase is of large molecular weight (S, 6--8), is resistant to thermal denaturation, is sensitive to N-ethylmaleimide, and is inhibited by high ionic strength. However, specific antisera that cross-react with mammalian DNA polymerase-alpha from different species fail to cross-react with the trypanosome polymerase.