Integrin receptors are well-known mediators of cell adhesion that also have a fundamental role in controlling the migration of cells through tissues. Among the numerous members of a still growing family, two particular molecular complexes have turned out to be of key importance in tumor cell invasion of basement membranes, the alpha3beta1 and alpha6beta4 integrins. In this Review, we will focus on the role of these two receptors and the mechanisms by which they influence the invasion process.