Fluorescence diagnosis has an increasing importance in different medical fields. In the presented paper, comparison of cystoscopy in white light with fluorescence cystoscopy after intravesical administration of 1 g of 5-aminolevulinic acid is presented.From the group of 63 persons examined, no difference between findings in white and blue light was found in 39 cases. In 21 patients more pathological spots were found in blue light (10 cases) or, in agreement with histology, pathology was detected in the blue light only (11 cases).The intravesical administration of 5-aminolevulinic acid had no side effects. Our study has definitely proved the advantages of fluorescence cystoscopy.