In vitro experiments were performed on human bladder carcinoma cells to evaluate the efficiency of photodynamic activity of protoporphyrindisodiumsalt encapsulated within liposomes. The bladder carcinoma cell line EJ 28, (Tumorba-nk Heidelberg) was grown on DMEM + 10% FCS + 2% Glutamine + 1% Penicillin/Streptomycin as a monolayer culture. In the log phase, cells were trypsinized, counted and inoculated into 35 mm-diameter multiwells at 105 cells/well and allowed to grow for 24 h. The cells were incubated for 1 h with 5, 10, 20 (mu) g/ml protoporphyrindisodiumsalt in liposomes. (DPPC/Cholesterol 7:3). After incubation cells were refed with complete medium and irradiated with 3 and 6 J/cm2. After irradiation, the cells were incubated for 2 days at 37 degree(s)C, then fixed, stained, counted and compared to the control group. Mean survival rates of 7.21%, 2.99%, 1.33% after irradiation with 3 J/cm2 and 4.3%, 1.48% and 0.88% after irradiation with 6 J/cm2 were found. By using a fluorescence microscope, we evaluated the intracellular uptake of protoporphyrindisodiumsalt in liposomes. The vesicular fluorescence pattern exhibited a concentration of photosensitizer in the nuclear membrane and adjacent parts of the cytoplasm as well as in the plasma membrane. By transmission electron microscopy marked changes were observed at the mitochondria with dissolution of the cristae and development of vacuols.