The deconvolution principle was used to evaluate the extent of absorption and first-pass elimination of selected drugs. In the first example, deconvolution of the portal blood profiles of etretinate (ET, a synthetic retinoid) indicated that there was significant gut-wall conversion of ET to acitretin (ETA, the primary metabolite of ET) during a 60-min intestinal perfusion of ET. In the second example, deconvolution was used to confirm that the extent of carbovir disappearing from the gastrointestinal lumen was matched by the extent of carbovir appearance in the portal blood. Thus, deconvolution has several important applications in the study of absorption and intestinal first-pass metabolism.