Treating primary hamster embryo cells with various classes of chemical carcinogens and mutagens leads to enhancement of transformation by simian adenovirus SA7. It appears that carcinogenic chemicals render the individual cells more sensitive to viral transformation, thus increasing the total number of cells integrating SA7 DNA. Enhancement of viral transformation appears to be a sensitive indicator for chemical agents with the potential to damage cell DNA by either direct or indirect means and thus may be useful as a screening tool to detect these chemicals in the environment. This report summarizes and compares the results for 134 chemicals (both carcinogenic and noncarcinogenic) assayed for enhancement of SA7 transformation, chemical transformation, and induction of DNA strand breaks and DNA repair synthesis. In addition, these chemicals are ranked by lowest effective concentration in the assay for enhancement of viral transformation.