Bioequivalence studies are generally performed as crossover studies and, therefore, information in the Intrasubject Coefficient of Variation (CV) is needed for sample size planning. Recently, a confusing point was noticed in calculating the Intrasubject Coefficient of Variation (CV) in crossover studies under the additive model (i.e. under normality assumption and the multiplicative mode (i.e under logarithmic distribution). The aim of this paper is to clarify this confusion. Methods used in calculating the Intrasubject Coefficient of Variation (CV) are reviewed in this paper from a statistical point of view.