Photodynamic therapy (PDT) is a dual therapeutic modality composed of a non toxic photo sensitizer (PS) and light of the appropriate wavelength.The PS is taken up to a high selectivity in malignant or abnormal tissue.After absorption of photons the PS produces toxic oxygen products which selectively destroy the target or emits fluorescence for diagnosis while leaving the interstitial tissue intact.The main indications are oncological, while fluorescence diagnosis in recent times gained wide attention following the slogan "to see and to treat".This method allows for example for a significant greater tumor resection in brain tumors (37 vs.67%), which translates also in a longer survival time.Besides phase Ⅰ/Ⅱ trials for PDT for malignant brain tumours, there are only few controlled clinical trials following tumour resection enrolling over 984 patients.Variations in treatment protocols, variation of PS and light dose make the evaluation scientifically difficult however the results compare favourably to the golden standard treatments.The median survival after PDT for primary glioblastoma multiforme WHO Ⅳ was 22 months and for recurrent GBM 9 months and 2 year survival 26,9 % : This compares to standard conventional treatment with XRT/Temodal and Gliadel to 26% and 15,6% moths for the 2 years survival and to the mean survival of 14,6 and 13,9 months, respectively.The combination ofPDD/FGR and PDT offers an exciting approach to the treatment of malignant brain tumours.PDT was generally well tolerated and side effects consisted of occasionally increased intracranial pressure and prolonged skin sensitivity against direct sunlight.The concept "to see and to treat" with PDD and PDT bears great potential in the treatment of brain malignancies.A phase Ⅲ trial is currently performed to verify the current data.