The photophysical properties and photodynamic effect of Zn(ii), Pd(ii), Cu(ii) and free-base 5-(4-(trimethylammonium)phenyl)-10,15,20-tris(2,4,6-trimethoxy phenyl)porphyrin (H2P) iodide have been studied in N,N-dimethylformamide (DMF) and in different biomimetic systems. The absorption, fluorescence, triplet state and singlet molecular oxygen production of the metal complexes were all referred to H2P. The photodynamic activity was first analyzed using 9,10-dimethylanthracene and guanosine 5'-monophosphate in N,N-dimethylformamide. The photooxidation processes were also investigated in benzene/benzyl-n-hexadecyldimethyl ammonium chloride/water reverse micelles. Photosensitization efficiency of these porphyrins was H2P approximately ZnP > PdP in homogeneous solution and ZnP > H2P > PdP in micelles, whereas no photooxidation effect was detected using the Cu(ii) complex. Human erythrocytes were used as a biological membrane model. The photohemolytic activity depended on irradiation time, sensitizer and concentration of the agent. When cells were treated with 1 microM sensitizer, the hemolytic activity was H2P > ZnP >> CuP. However, it was H2P > ZnP approximately CuP using 5 microM of the respective porphyrin. Although CuP could undergo a type I photoreaction, in all cases the photohemolytic effect considerably diminishes in anoxic conditions, indicating that an oxygen atmosphere is required for the mechanism of cellular membrane damage. The behavior of these amphiphilic metallo porphyrins provides information on the photodynamic activity of these agents in biomimetic microenvironments.