The two-period repeated measurements crossover design is often employed in clinical trials. This paper presents a unified approach for the statistical analysis of such a design that clarifies the testing procedures and assumptions employed under different conditions. It is shown how the data may be transformed so that it could be analyzed under the framework of a completely randomized repeated measurements design. Applications are given to a comparative bioavailability trial for attainment of steady state levels and to a clinical trial to compare the effects of two hypolipidemics.