The GTP-binding protein Rho regulates the assembly of focal adhesions and their associated bundles of actin filaments. Two different lines of research have converged to reveal how Rho might regulate assembly of these structures. One approach has been the identification of downstream effectors of Rho, whereas the other has been the exploration of the role of contractility in promoting assembly. It is now apparent that Rho is a key regulator of actomyosin-based contractility in nonmuscle cells and that contractility, combined with adhesion to a rigid substrate, leads to the formation of both stress fibres and focal adhesions.