Abstract A comparison of the polynuclear aromatic compound (PAC) content and dermal carcinogenicity was made for a series of complex oil mixtures. Results showed a significant correlation (r2 = 0.76) between the 3–7 ring PAC content and the carcinogenic potency, as determined in a mouse skin-painting bioassay, for oil samples ranging from those with median (50% recovered) boiling points above –500°F to those with initial boiling points of –1070°F. Two variables not considered in the original correlation study, oil viscosity and oil dermal penetration rate, were subsequently measured and their correlation with the carcinogenic potency of the oils determined using simple and multiple regression techniques. Although a weak correlation was observed between oil viscosity and the dermal penetration rate of 3H-benzo[a]pyrene from the oils (co-linear variables), no statistically significant correlation was observed between viscosity or penetration rate and carcinogenic potency. It is suggested that the repeated d...