The primary tumors and adjacent normal tissues in a cohort of 52 patients were analyzed by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) for the expression of miR-205 and SMAD4. The functions of miR-205 and its molecular link to SMAD4 were also investigated in cell lines and transplanted tumor models of lung carcinoma in mice. This evidence concerns the gene SMAD4 and lung carcinoma.