We examined 70 fresh frozen sections of primary non-small cell lung cancer using a monoclonal antibody for DNA polymerase alpha (POL alpha). The tumors were divided into two groups; those with more than 5% of POL alpha positive cells were designated as POL alpha (+), while those with less than 5% were POL alpha (-). POL alpha (+) tumors were obtained in 33 (47%) cases. The incidence of POL alpha (+) in male patients was statistically higher than in females (P < 0.01). The incidence also correlated with the T(tumor) status; T1 < T2, T1 < T4, with a significance (P < 0.05). Based on data on 70 patients, the 5-year survival rates of POL alpha (+) and POL alpha (-) were 36% and 63%, respectively (p < 0.05). In 48 patients with adenocarcinoma, the 5-year survival rates of POL alpha (+) and POL alpha (-) were 25% and 60%, respectively (P < 0.05). In addition, in 26 patients with a tumor size of less than 3 cm, the 5-year survival rates of POL alpha (+) and POL alpha (-) were 13% and 74%, respectively (P < 0.01). To compare the prognostic significance of the variables, a multivariate analysis was used to show significance for survival in POL alpha (p < 0.05). Our data show that in non-small cell lung cancer, POL alpha expression is associated with the extent of malignancy and survival. Therefore, POL alpha is considered to be a useful prognostic parameter.