Objective: To investigate the correlation between CT appearance and expression of p53 protein in peripheral lung cancer. Methods: The expression of p53 protein was examined by means of SP immunohistochemical technique in 32 cases of peripheral lung cancer. Their correlation with the preoperative CT appearance was analyzed retrospectively.Results: The expression of p53 protein was correlated with tumor size, lobulation, cavitation, pleural indentation and mediastinal lymph node enlargement, but not with spiculation. Tumor with maximum diameter greater than 3 cm or with the presence oflobulation, cavitation, pleural indentation or mediastinal lymph node larger than 10 mm in short axis had a relatively higher level of p53 expression. Conclusion: CT signs of peripheral lung cancers are valuable not only in differentiating cancers from benign lesions, as known before, but also in providing further information for the malignant potential of cancers. Larger tumor size, lobulation, cavitation, pleural indentation, and mediastinal lymph node enlargement may be likely related to a higher degree of malignant potential and more aggressive tumor behavior.