The value of the SENCAR mouse for testing tumorigenic properties of complex mixtures on mouse skin was studied. Seven complex mixtures were obtained as dichloromethane extracts of collected particulate emissions from three diesel-fueled automobiles, a heavy-duty diesel engine, a nonleaded gasoline-fueled automobile, a coke oven battery, and a roofing tar pot. These emissions were applied topically at multiple doses to both male and female SENCAR mice that were subsequently promoted with 12-0-tetradecanoylphorbol 13-acetate. Two statistical analyses were applied to the data to rank the samples and to provide 95% confidence intervals.