Purpose: To investigate the relationship between the expression of ET, the content of DNA and prognosis in primary lung cancer. Methods: The expressions of ET and the contents of DNA in 66 cancer specimens of different pathological grades were studied by immunohistochemistry and image - analysis technique, all cases were followed up more than 2 years. Results: The positive rate of ET in lung cancer was 73%, which was significantly higher than that in benign bronchial disease (P0.05). The content of DNA in the positive group of ET was significantly higher than that in the negative group (P