A 3-4S DNA polymerase was partially purified from a fraction with endogenous RNA-directed DNA polymerase activity isolated from normal chicken embryos. The activity of this 3-4S DNA polymerase was not neutralized either by an antibody prepared against DNA polymerase purified from avian myeloblastosis virus or by an antibody prepared against a 10S DNA polymerase purified from the soluble fraction of chicken embryos. After removal of ribonuclease activity, the 3-4S DNA polymerase could utilize avian RNA tumor virus RNA as a template-primer. The response of this 3-4S DNA polymerase to synthetic template-primers was very similar to that of DNA polymerase from avian sarcoma virus and different from that of soluble chicken DNA polymerase. The existence of a chicken DNA polymerase which can utilize RNA as well as DNA as a template-primer for DNA synthesis suggests that this type of DNA polymerase could play a role in information transfer from RNA to DNA in normal cells, as suggested by the “ protovirus hypothesis. ”