Alpha 1-Proteinase inhibitor[PI] was known as a major protective enzyme against to excessive hydrolytic and proteolytic reaction. So, it was suggested that Alpha 1-PI may implicated in growth of bronchogenic cancer. This study was undertaken to investigate the role of Alpha 1-PI in local invasion of bronchogenic cancer. Three groups of patients were studied; Preliminary research group of 15 bronchogenic cancer patients, Main research group of 13 bronchogenic cancer patients and Normal control group of 10 nephrectomy donor. Serum Alpha 1-PI level was observed in each group of patients during pre-and postoperative days. Pre-operative serum Alpha 1-PI level in preliminary research group [329.2$pm$14.21mg/dl]and main research group[406.2$pm$39.30mg/dl] were higher than in normal control group[236.2$pm$19.55mg/dl] significantly[p<0.005]. Serial Alpha 1-PI level in each group during pre-and postoperative days shows peaked at 3rd. postoperative day in preliminary and main research group, thereafter decreased gradually. Immunohistochemical study for Alpha 1-antitrypsin[A1AT] was carried out by ABC[avidin-biotin peroxidase complex] method using Alpha-1 antitrypsin DAKOR to tumor tissues of 13 lung cancer patients in main research group. 6 cases[46.2%, squamous cell ca.;5, adenocarcinoma;1] of above 13 cases show positive immunoreactivity for A1AT. In conclusion, alpha 1-PI and elastase are disclosed that have defined actions for lung cancer growing or spreading.