ABSTRACT: The goal of this presentation is to discuss results from a series of recent clinical studies (J. Pharm. Sci. 105:996-1005, 2016) and considerations for BCS class 3 biowaivers. In a series of recent clinical studies, the objective was to assess the impact of larger than conventional amounts of 14 commonly used excipients on BCS class 3 drug absorption in humans. Cimetidine and acyclovir were used as model class 3 drugs across three separate four-way crossover bioequivalence studies (n=24 each) in healthy human volunteers, denoted study 1A, 1B, and 2. Overall, 12 common excipients were found in large amounts to not impact BCS class 3 drug absorption in humans, such that these excipients need not be qualitatively the same nor quantitatively very similar to reference, but rather simply be no more than the quantities studied here. Meanwhile, for each HPMC and microcrystalline cellulose, BCS class 3 biowaivers require these two excipients be qualitatively the same and quantitatively very similar to the reference..