The hypothesis that lung cancer mortality can be diminished by radiographic screening is founded on several implicit assumptions. Some are debated, eg, that overdiagnosis is so infrequent that its effect can be discounted and screening can be cost-effective. Others, although unproven, appear axiomatic, eg, that the incidence of lung cancer is fixed except for minor secular changes; that increased survival of screen identified early lung cancer will necessarily reduce mortality; and that increased identification of surgically curable lung cancers will achieve a reciprocal reduction in the number of advanced and surgically incurable lung cancers. Some premises appear to be not only self-evident, but tautological, eg, that the prognosis of stage I lung cancer equals the prognosis of stage I lung cancer. Each of these implicit premises, and more, are open to question; they are the subject of this review.