[en] Fluorescence bronchoscopy with a violet laser and image intensifier has been developed for imaging the red fluorescence of a tumor-specific agent, hematoporphyrin derivative, that has been injected before the examination. The instrument was developed to localize carcinoma in situ and early, small bronchogenic tumors diagnosed by sputum cytology but invisible on chest x-ray and conventional bronchoscopy, in underground uranium miners and others at risk for lung cancer. In addition to the imaging devices, a video system including a processor and electronics for digital background image subtraction has been developed to enhance contrast. A ratio fluorometer and a rapid-scan spectrum analyzer have been designed for quantitative measurements of fluorescence intensity and dependence on dosage and time after injection of the fluorescent agent. Clinical trials demonstrate detection of carcinoma in situ, and the true positive rate should be improved by the new instrumentation and optimization of time delay and dosage. 14 references, 6 figures