BACKGROUND: The cyclin D1 gene is one of the most frequently amplified chromosomal regions(11ql3) in human carcinomas. In laryngeal and head and neck carcinomas, its overexpression has been shown to be associated with advanced local invasion and presence of lymph node metastases. Cyclin D1 may therefore play a key role in cell growth regulation and tumorigenesis. Lung cancer is a worldwide problem and in many contries it is the most lethal malignancy. As relapse is frequent after resection of early stage non-small cell lung cancer, there is an urgent need to define prognostic factors. PURPOSE: This study was undertaken to evaluate the prognostic value of the cyclin D1, that is one the G1 cyclins which control cell cycle progression by allowing G1 to S phase transition, on the patients in radically resected non-small cell lung cancer. METHOD: Total Si cases of formalin-fixed paraffin-embedded blocks from resected primary non-small cell 11mg cancer from January 1., 1983 to July 31, 1995 at Hanyang University Hospital were available for both clinical follow-up and immunohistochemical staining using monoclonal antibodies for cyclin D1. RESULTS: The histologic classification of the tumor was based on WHO criteria, and the specimens included 45 squamous cell carcinomas, 25 adenocarcinomas and 11 large cell carcinomas. Cyclin D1 overexpression was noted in 26 cases of 81 cases tested (30.9%). Cyclin D1 expression was not significantly associated with cell types of the tumor, pathological staging and the size of the tumor. But cyclin D1 overexpression was significantly correlated with positive lymph node metastasis(p=0.035). The mean survival duration was 22.76+/-3.50 months in cyclin D1 positive group and 45.38 +/- 5.64 months in cyclin D1 negative group. There was a nearly significant difference in overall survival Between cyclin D1 positive and negative groups(p=0.0515) in radically resected non-small cell lung cancer. CONCLUISON: Based on this study, cyclin D1 overexpressiom appears at important poor prognostic indicator in non-small cell lung cancer and may have diagnostic and prognostic importance in the treatment of resectable non-small cell lung cancer.