SUMMARY Screening for lung cancer is expected to lead in more cases diagnosed in early stage and subsequent reduction in mortality rates. Randomized trials during the seventies showed that screening with chest x-ray and/or sputum cell cytology does not offer advantage in survival. Nevertheless, in the eve of the century, there is enough evidence to support the growing optimism that new imaging techniques and examination of sputum samples for the presence of biological markers of carcinogenesis in bronchial epithelium will contribute to the development of more powerful screening methods for early detection of bronchogenic carcinoma. In the present report we discuss the results of preclinical and preliminary clinical trials in this field. We also present in brief current theories for bronchial carcinogenesis, on which contemporary attempts for early diagnosis using sputum samples are based. Pneumon 2000, 13 (3): 196-208