Simulated data using a linear two-compartment body model (2CBM) with drugs having different absorption characteristics and dosage forms with different dissolution rates were used to evaluate the inherent problems of pharmacokinetic data analysis (flip-flop phenomenon and vanishing exponential terms). When absorption from solution is slow or release from the solid dosage form is rate limiting, the characteristic nose of the 2CBM was lost and a one-compartment model prevailed. After the 2CBM disposition kinetic parameters were obtained from solution data, absorption kinetics were evaluated by the Loo-Riegelman method. The data were also evaluated by the statistical moments method. The statistical moments method consistently demonstrated superiority in regard to providing reliable results and ease in calculation. The information provided can be particularly useful for in vivo-in vitro correlation.