We continued an investigation of the structure of mammalian DNA polymerase Alpha. Our current results emphasize a 195,000-Mr polypeptide in growing calf and monkey cells that appears to be an abundant Alpha-polymerase constituent. This protein is obtained directly from crude soluble extracts of growing cells by immuno-precipitation with monoclonal antibody to calf Alpha-polymerase. Further validation and improvement of the activity gel method for study of DNA polymerase catalytic polypeptides as conducted, and this method was used to demonstrate induction of the about 120,000 - Mr Alpha-polymerase polypeptide in resting monkey cells by SV40 infection and for analysis of Beta-polymerase levels in human cells in culture. Efforts were continued to obtain plasmid cDNA clones with sequences homologous to Alphapolymerase genes.