The molecular association behavior and the interfacial mechanism of polyamidoamine (PAMAM) dendrimers for anionic porphyrins and bioactive species at the polarized water I 1,2-dichloroethane (DCE) interfaces as a model of a biomembrane system were studied through potential modulated fluorescence (PMF) spectroscopy. In aqueous solutions, zinc (II) porphyrin that associated with the dendrimers was stabilized without protolytic demetalation in a wide range of pH. On the other hand, the free base porphyrin was readily protonated following the foimation of J-aggregates of diprotonated species. PMF measurements at the interface revealed that the dendrimers incorporating porphyrin molecules were transferred across the positively polarized interface accompanied by an adsorption process, whereas the porphyrins released from the dendrimers were transferred at the negatively polarized interface. In addition, the ion-association stability between the dendrimer and the porphyrin was quantitatively estimated based on the negative shift of the transfer potential of the porphyrins. Although ionizable drugs were not effectively associated with the dendrimers in the aqueous solutions, the PMF results of the fluorescent dipyridamole (DIP) indicated that the interfacial mechanisms of DIP species were significantly modified by the dendrimers, depending on the pH conditions. Flavin derivatives were effectively associated with the dendrimer in aqueous solution. The interfacial adsorption of the anionic flavin derivatives was inhibited by forming associates with the dendrimer, while the associates were transferred across the interface in the positive potential region.