Carcinoma of the lung is the leading cause of death from malignancy in this country. Twenty percent of patients with lung carcinoma are asymptomatic early in the course of the disease. Survival rates are much better when lung carcinoma is discovered at the asymptomatic or radiographically occult stage, therefore improved screening methods should be investigated. Many tumors in the tracheobronchial tree shed malignant cells into the bronchi and sputum cytology has been of value in the early diagnosis of carcinoma of the tracheobronchial tree. Thousands of patients are intubated daily. During endotracheal anesthesia, secretions are stimulated in the tracheobronchial tree and endotracheal or tracheostomy tubes are coated with these secretions. In a preliminary study, the cytology examination of the secretions adherent to 50 endotracheal tubes suggests that endotracheal and tracheostomy tube cytology will prove to be a reliable, noninvasive and cost-effective means of screening high risk patients for occult primary carcinomas of the lung and upper aerodigestive tract.