The effect of drug concentration on in oitro release of salicylic acid from a series of ointment bases was investigated. The bases were commercially available vehicles containing lanolin and/ or lanolin derivatives and formed stable water-in-oil or oil-inwater emulsions. Release tests were performed both with the anhydrous and with the emulsion forms of the bases, a t varying salicylic acid concentrations (0.5-5.0% w/v), and involved the use of silicone rubber membranes. The release of salicylic acid from the bases was in agreement with a reported diffusional model. A linear relationship between release rate, q / A , and drug concentration in ointments existed when the drug was completely dissolved in the vehicles. The method reported is of potential utility for the determination of drug solubility in ointments and for the evaluation of the optimal drug concentration in topical vehicles. The relationships among type of vehicle, drug concentration, drug solubility, and release rate are discussed. Keyphrases I I Vehicles (lanolin and lanolin derivatives)-in uitro release of salicylic acid, influence of drug concentration Ointment bases-influence of drug concentration on in uitro release of salicylic acid 0 Drug concentration-influence on in oitro release of salicylic acid from ointment bases 0 Lanolin and derivatives as ointment vehicles-influence of drug concentration on in uitro release of salicylic acid