Even of those few patients who are operated because of bronchial cancer up to a quarter develop a recurrence. One reason is certainly that tumor-cells already present at the time of surgery are bronchoscopically invisible. Fluorescence methods might be able to detect these malignant cells. For patients with post-surgical recurrences the therapeutical choices are limited due to the loss of parenchyma. Photodynamic therapy (PDT) with the hematoporphyrine derivative Photofrin is one laborious but promising option. Based on an argon-dye laser we have developed a combined system for the diagnostical measurement of autofluorescence and Photofrin-induced fluorescence at 488 nm and the therapeutical PDT at 630 nm. Under the excitation with blue light from the argon laser, differences in the autofluorescence of malignant and benign cells can be distinguished. Following the injection of Photofrin a spectrum peak at 628 nm clearly delineates tumor cells. In six out of twelve patients with post-surgical recurrences a single PDT course resulted in tumor eradication. With additional PDT courses and brachytherapies local tumor control could be achieved in all cases. The general photosensitivity and the necessary light protection were tolerated by all patients. In order to avoid severer complications such as asphyxia, obstruction of bronchi and pneumotharaces resulting from fibrin-plugs and necrotic tissue following PDT must be considered. Especially in patients with pneumonectomy a careful surveillance and debridement is mandatory.