A discrepancy has been noted in the relationship between the relative skin permeabilities of phenols and their lipophilicities as expressed in commonly used octanol/water partition coefficients. The permeability coefficients of 4-nitrophenol and several other phenols through skin and a model lipophilic membrane made of silicone rubber were found to be independent of concentration, ruling out concentration dependent molecular aggregation as the cause of the partitioning-permeability incongruity. An unexpectedly low permation rate was observed for the diffusion of 4-nitrophenol through the synthetic, silicone rubber membrane, confirming the phenol's anomalous position in permeability relative to the octanol/water partitioning scale. However, when o/w partition coefficients for the phenolic compounds based on either n-hexane, methylene chloride, chloroform or silicone rubber as the water immiscible phase are used, permeability coefficients for the skin and the synthetic membrane followed expected permeation-partitioning dependencies.