Photodynamic therapy is based on the capacity of certain substances to preferentially stain neoplastic tissues in respect to healthy tissues, and on the property of such substances to produce cytotoxic agents when excited by light of an appropriate wavelength. The authors demonstrate the first attempts to photoradiant therapy in the treatment of human gliomas utilizing a hematoporphyrin derivative injected i.v. as a sensitizing drug. A He Ne Laser (632,8 nm) was used in order to trigger the photodynamic process. Immediately after surgical removal of the glioma the residual tumoral bed was exposed to the action of the Laser in order to provoke necrosis of the remaining neoplastic cells. Necrosis even if partial of the residual tumor was effected. Better and more definite results may be obtained in the future utilizing a Laser connected with fiber optics consenting an in-depth light penetration.