We have studied the autofluorescence and induced fluorescence in renal tumors and healthy renal tissues in 90 patients with renal cell carcinoma from the National Scientific Institute of Urology in the period from January 2012 up to June 2013. “Alasens” (5-aminolevulenic acid hydrochloryde) was shown to be selectively accumulated in the tumor cells, to transform into protoporphyrine IX and to fluoresce against the blue light. Own fluorescence excited by the light with a wave length 630 nm and also in the course of fluorescence diagnostics (FD) at the wave length 460 nm could not be a reliable criteria of the presence or absence of the tumor and could not influence the results of the secondary fluorescence. At that time, induced fluorescence allows the tumor identification; good contrast at the border of tumor and healthy tissue permits the identification of the tumor boundaries using the fluorescence directly at time of operation. In the dosage 20 mg/kg of body weight 5-aminolevulenic acid could be safely used in laparoscopic and open partial nephrectomy without any clinically or laboratory recognizable toxic effects.