Principal components analysis (PCA) and multivariate regression analysis have been employed to study the relationship between a series of calculated physicochemical properties of terpenes (solubility parameter, calculated logK_oct, molecular mass, molecular volume, calculated surface tension, scaled H-bonding donor and acceptor values, non-carbonyl carbons per molecule) to the permeation enhancing activity of each terpene for propranolol HCl across newborn pig skin. With PCA, a smaller number of new variables (five principal components) were used as predictors in regression analysis in order to predict the enhancing activity of terpenes on the permeation of the model drug propranolol HCl. A fairly high coefficient of determination (R² = 0.87) suggested that the resultant regression equation was able to adequately predict trends in the enhancing activity of the terpenes. PCA results suggested the importance of a combination of the physicochemical properties on the enhancing activities of the terpenes. A suitable balance between these terpene properties is required to lead to a considerable enhancement of propranolol HCl penetration.