Cadherins are Ca2+-dependent cell-cell adhesion molecules, and are involved in the formation and maintenance of the histo-architecture. Using a combination of biochemical and immunohistochemical methods, we analyzed the expression of cadherin-catenin complexes in 37 non-small cell lung carcinomas. In 19 cases, decreased expression of E-cadherin protein was observed. In 12 of them, decreased expression of alpha-catenin protein was also observed. Thus, decreased expression of alpha-catenin was apparently preceded by decreased expression of E-cadherin. In no cases was decreased expression of beta-catenin observed. In the 12 cases in which mRNA expression was analyzed by Northern blot analysis, decreased expression of mRNAs for E-cadherin and alpha-catenin was observed in 11 and 9 cases, respectively. In cases with reduced E-cadherin and alpha-catenin expression, immunohistochemistry revealed two types of staining pattern for the proteins. In the first type, almost all the cells in a tumor were stained weakly (homogeneous pattern). In the second type, different percentages of cells were stained strongly, the rest being almost negative for the staining (heterogeneous pattern).