The effect of atropine (ATR), a parasynpatholytic agent, on the intestinal absorption of salicylamide (SAM) was studied using the absorption kinetic model proposed by Winne et al. The disappearance of SAM from perfusate and the appearance in intestinal blood were determined using perfused intestinal loop of the rat in vivo. The results showed that the absorption of SAM was simulated by the four compartment model consisting of luminal, interstitial, blood and serosal compartments. The model was assumed to have three rate determining factors, namely mucosal membrane permeability, clearance by blood flow and serosal membrane permeability. ATR decreased the absorption of SAM by decreasing the clearance factor relating to intestinal blood flow and increased the fraction of the transported amount of SAM from interstitia1 space to serosal compartment.