Extract of Boswellia sacra (incense tree), the main active components of which are boswellic acids, is used for the treatment of rheumatoid arthritis and gout. Boswellic acids suppress leukotriene biosynthesis in neutrophilic granulocytes by non-redox, noncompetitive inhibition of 5-lipoxygenase. Representing pentacyclic triterpenoids, boswellic acids are characterized by poor solubility in water and are highly lipophilic (1og P = 7–10.3). Bioavailability of the B. sacra (BS) extract has been studied using a new method developed for estimating and predicting the possible absorption of medicinal substances in vivo, which is based on the establishment of a correlation between the data obtained in vivo and in vitro. The validity and applicability of the proposed method is demonstrated. Release of four individual boswellic acids from BS extract has been studied in vitro using a nonconventional two-phase system simulating conditions in the gastrointestinal tract. Based on these data, the dissolution rate constants of boswellic acids have been calculated. In addition, the parameters of pharmacokinetics of ketoacids in vivo have been determined and a correlation between these parameters and the rate of release in vitro has been studied. It is established that there is a strong correlation between the results obtained in vivo and the dissolution of boswellic acids in the model two-phase medium in vitro, which makes possible prediction of the pharmacokinetic profiles of individual acids upon per os administration of BS extract.