The E-cadherin-catenin complex proteins function in cell-cell adhesion and have been reported to be dysregulated in various human malignancies. Beta catenin is a cytoplasmic protein that associates with tyrosine kinase receptors and modulates cytoskeletal dynamics. It also plays a role in the Wnt signaling pathway. During neoplastic transformation, the phosphorylation of beta-catenin causes a loss of intercellular adhesions resulting in increased tumor cell motility and invasiveness. Tissue sections from 100 cases of non-small cell lung cancer (NSCLC) were immunostained with a monoclonal beta-catenin antibody. There were 47 squamous cell carcinomas (SCC) and 53 adenocarcinomas (AC) in the study group. Plasma membrane/cytoplasmic beta-catenin immunoreactivity was scored for intensity and distribution and correlated with tumor stage, grade and survival. Plasma membrane/cytoplasmic immunoreactivity for beta-catenin protein was observed in 71 (71%) of 100 NSCLC. 44 (94%) of 47 SCC and 27 (51%) of 53 AC expressed beta catenin. On univariate analysis, loss of beta catenin expression correlated with high tumor stage (p = 0.025), large tumor size (p = 0.02) and decreased patient survival (p = 0.04). The loss of beta catenin expression associated with high grade NSCLC reached near significance (p = 0.07). On multivariate analysis, the loss of beta catenin expression independently predicted shortened overall patient survival in NSCLC (p = 0.05). Beta catenin expression loss is associated with advanced tumor stage and is an independent predictor of shortened patient survival in NSCLC.