The reported frequency of missed diagnoses has varied significantly in the literature. In one report from the Mayo Lung Project,690% of peripheral carcinomas (45 of 50) were visible in retrospect despite the fact that three physicians (radiologists and pulmonologists) had prospectively reviewed all chest radiographs. Twenty-seven carcinomas had been visible for ≤ 1 year, but 4 carcinomas had been visible for > 2 years (a patient in the screening trial had chest radiographs performed every 4 months). Seventy-five percent of the perihilar carcinomas were visible in retrospect (ie, 12 of 16 carcinomas). Similarly, two thirds of the lung cancers were visible in retrospect in the Memorial Sloan Kettering Cancer Center screening trial conducted simultaneously with the Mayo Clinic Trial.7 Austin and colleagues,8from New York City, reported on 27 lung cancers that had been missed on previous chest radiographs. The mean diameter of the missed lesion was 1.6 cm. Five cancers (19%) were < 1 cm, 13 cancers (50%) were 1.0 to 1.9 cm, and 5 cancers (19%) were 2.0 to 2.9 cm at the time that they were missed. The interval to eventual diagnosis was 10 months, with a range of 0.2 to 47 months. Quekel and colleagues9reviewed all cases of proven lung cancer from 1992 to 1995 in a large teaching hospital in the Netherlands. The lesion was missed in 49 of 259 patients (19%) with NSCLC presenting as a nodular lesion. The median diameter of the missed lesion was 1.6 cm (range, 0.6 to 3.8 cm). The median delay in diagnosing the missed lesion was 472 days (range, 7 to 3,233). The miss rate for lesions ≤ 10 mm was 71%, for lesions between 10 and 20 mm the miss rate was 29%, and for lesions 21 to 30 mm the miss rate was 24%. A major reason for the limitation in detecting lung lesions is that 25% of the lung parenchyma on the standard posteroanterior chest radiograph is hidden by normal structures such as the heart, mediastinum, and diaphragm.10 In summary, these studies make it very clear that a chest radiograph is not a sensitive tool for detecting early lung cancer, especially those < 2 cm in size.