Since tumour progression is dependent on the ability of malignant cells to interact with the extracellular matrix (ECM), we have investigated the significance of beta 1 and beta 3 integrins for migration of lung cancer cells to components of the ECM. In an in vitro hapto- and chemotactic assay system, five cell lints representing the major types of lung cancer were examined: adenocarcinoma (WART); squamous cell carcinoma (U-1752); small cell lung cancer (SCLC) (U-1906, 054 A) and large cell lung cancer (LCLC) (U-1810), Flow cytometric analyses were performed to characterize their integrin expression, U-1906, 054 A, WART and U-1752 all expressed beta 1 integrins whereas U-1810 did not, However, U-1810 and U-1752 expressed beta 3 integrins, All cell Lines except U-1810 and U-1752 showed hapto- and chemotactic motility to fibronectin, laminin and type IV collagen and this motility was beta 1 integrin-dependent except in the case of U-1810, However, the hapto- and chemotactic responses differed markedly between the separate cell lines and there was no distinct pattern to separate non-small cell lung cancer (NSCLC) from SCLC, No or very little migration nas seen in control experiments with bo cine serum albumin (BSA) or serum-free medium alone, indicating that the migration of the lung cancer cells require adhesion molecules, soluble or substratum bound. We have found the involvement of beta 1 integrins in lung cancer cell migration in vitro ton;ards fibronectin, laminin and type IV collagen except in the case of U-1810. The U-1810 cell line clearly differed from the rest of the cell lines by larking expression of beta 1 integrins.