Sputum cancer cell examination (sputum test). Different steps should be taken according to different situations in the diagnostic workup. I. Negative X-ray and negative sputum examination 1. Any person without symptoms but with three major high-risk factors (male, age ≥45 years and smoking >400 cigarettes/year) should undergo 70-100mm fluorescent microscopic X-ray or chest fluoroscopy and sputum cytology examination half-yearly. 2. Anyone with hemoptysis or/and dry choking cough with three major high-risk factors should undergo repeated sputum cytology and be given regular anti-inflammatory treatment at the same time; fiberoptic bronchoscopy (fibronectomy) and televisual fluoroscopy can be considered. If repeated sputum examination or microscopy is still negative, it should be reviewed every two months and adhered to for one year. 2.X-ray negative, sputum positive 1.Exclude upper respiratory tract and esophageal cancer 2.Perform fiberoptic bronchoscopy, strive to peer into sub-sub-segments, and if there is suspicious local mucosal thickening, roughness or blood stains, brush inspection, rinsing or puncture of bronchial wall mucosa should be performed in the area to search for cancer cells. If local unevenness or roughness is found, it should be considered for biting biopsy. 3.Conduct TV fluoroscopy and change the body position, focusing on small nodule foci in hidden areas. 4.If no lesion is found by the above examinations, sputum, electrodialysis and fibrinoscopy should still be repeated every two months. CT examination can also be performed, and subdivision can be made at suspicious places. Regular re-examination should be continued for not less than one year. C. Positive X-ray and negative sputum 1. Those with segmental or lobar pneumonia or obstructive pneumonia and suspected central lung cancer should undergo fibrinoscopy, including trans-fibrinoscopic biopsy (TBB), or selective bronchography; and repeatedly strengthen sputum examination. 2. Local tomography should be performed for mass or nodal lesions. Transbronchoscopic lung biopsy (TBLB), or percutaneous lung biopsy, or aspiration for cytological diagnosis can be performed if available. 3.Continuous sputum examination should be done at least twelve times. 4.If repeated sputum examination is still negative, and x-ray is highly suspicious of lung cancer, dissection and frozen section biopsy should be performed. 4. Positive X-ray and positive sputum test 1. Active pre-surgical preparation. 2.If regional lymph node enlargement is suspected, frontal and lateral oblique stratification films can be taken. For limited stage small cell lung cancer, CT and lateral tilt stratification film, liver ultrasound, bone isotope scan and bone marrow aspiration into biopsy smear should be routinely used in large hospitals to facilitate the formulation of treatment plan.