Lung cancer is the second most common cancer and the leading cause of cancer death in both men and women. The purpose of the study is to explore the distribution of the 4 major histologic types of lung carcinoma and the incidence of lung cancer with reference to all other sites of cancer. The clinical and histopathologic data of 4,439 patients with lung carcinoma between January 1980 and December 2003 were reviewed. Adenocarcinoma has become the most frequent histologic type in men and women (36.8% and 46.5%, respectively), followed by squamous cell carcinoma (31.6% and 25.4%, respectively). The incidence of large cell (undifferentiated) carcinoma in men and women is 18.0% and 9.9%, respectively. The incidence of small cell carcinoma in men and women is 13.7% and 18.3%, respectively. In addition, analysis of our data indicates that lung cancer rate is decreasing, relative to all other primary cancer sites. The results of this study suggest that the incidence of lung cancer has decreased in comparison with other sources of cancer in southern Texas. This observation is consistent with the current national trends. In addition, there are significant changes in the distribution of the major histologic types of lung cancer. The results of this study may portend important changes in the selection of targeted therapy and patient management.