Monolayers of endothelial cells respond to physical denudation with a characteristic sequence of lamellipodia extrusion, cell migration, and cell proliferation Basic fibroblast growth factor (bFGF) has been implicated as a necessary component of this process addition of exogenous bFGF enhances monolayer regeneration both in vitro and in vivo, and monolayer regeneration can be inhibited in vitro by treatment with neutralizing antibodies raised against bFGF Centrosome reorientation from a random location to one preferentially situated between the nucleus and the denudation edge has been postulated as a mechanism essential for cell polarization and subsequent migration This present study examined the effects of a polyclonal antibody to bFGF and suramin on monolayer regeneration, actin microfilament staining, and centrosome orientation at the wound edge of partially denuded bovine large vessel endothelial monolayers. Treatment with anti-bFGF or suramin abolished monolayer repair in these cultures Cells at the denudation edge showed altered actin staining patterns and reduced lamellipodia extrusion, and there was complete inhibition of centrosome reorientation in treated cultures Monolayer repair and centrosome reorientation could be restored by addition of exogenous bFGF in antibody but not suramin treated cultures Recent evidence suggests that preferential centrosome location in migrating cells may be a consequence of lamellipodia protrusion and cell spreading, rather than an indication of cell polarization However, these results indicate that agents which interfere with bFGF availability prevent endothelial monolayer regeneration via mechanisms involving cell spreading and/or centrosome reorientation