A correlation for predicting dermal carcinogenicity of petroleum oils in laboratory animals has been developed using two simple analytical tests. The tests are the Food and Drug Administration test (FDA) commonly used to measure white oil purity, and a viscosity test. In the correlation, FDA is a measure of aromaticity, and viscosity is used to account for molecular weight. The FDA test alone appears to be comparable to other predictors now in use, but incorporating viscosity significantly increases the accuracy of predicting dermal carcinogenicity. A formula is proposed, using both the FDA test results and viscosity, that predicts the percentage of mice which will develop neoplastic skin tumors.