The two major steps in our study on the treatment of bladder tumors by photodynamic therapy (PDT) were the development of a new bladder tumor model in Fischer rats by implantation of tumor cells and the use of fluorescence spectroscopy, a semi-quantitative and non-invasive method, in order to determine the time after general or local administration of a photosensitizer when the tumor:normal bladder ratio was at its highest. 5-Aminolevulinic acid (5-ALA) (250 mg/kg body weight) was injected i.p. or instilled directly into the bladder cavity for 1, 2 or 4 h and fluorescence was measuredin situon normal and bladder tumor tissues every 30 min for 8–10 h after administration, with a special miniaturized optical-fiber captor. The better tumor:normal bladder ratios were 2.85±1.2 at 3.5 h after i.p. administration and 3.96±1.04 after bladder instillation for 4 h, respectively. These results were confirmed by fluorescence microscopy. PDT with the same dose of 5-ALA as in this pharmacokinetic study must also be carried out in order to compare the toxicity of the two administration routes of the photosensitizer and to determine which one is the better for this bladder tumor model.