Photodynamic therapy (PDT) with porphyrin derivatives (haematoporphyrin and dihaematoporphyrin äther/ester) and laser light of the wavelength 640 nm, is a new procedure for the treatment of carcinomas. This form of therapy is selective, can be applied through the bronchoscope, and is aimed at accomplishing curative elimination of central tumours of the lung. To date, we have successfully applied PDT in four selected patients. Our first patient was treated in April, 1987. The irradiation modalities and the clinical course are described.