Integrins are cell-surface receptors which are involved in cell-matrix and/or cell-cell adhesion. They have been suggested to play a role in tumor invasion and metastasis. We examined the expression of various integrin subunits in normal and cancer cells of the lung using 33 human lung cancer cell lines as well as 6 lung cancer samples from which tumor cell lines could be established. This study clearly demonstrated that changes in the expression of certain integrins occur frequently in lung cancer, especially in small cell lung cancer. Loss of the alpha 1 subunit of the beta 1 integrin family appears to be the most prominent change, although loss of other integrin subunits such as alpha 2 or emergence of some integrin subunits such as alpha v can also be observed. These results suggest that changes in integrin expression may contribute to the invasive and/or metastatic behavior of lung cancer.