Cofilin is one of the major actin depolymerizing proteins in eukaryotic cells and involved in many membrane modulating activities, such as cell growth and motility. Here we examined whether cofilin is activated upon Ca2+ regulated noradrenalin secretion from bovine adrenal chromaffin cells. We found that triggering exocytosis by nicotine causes a dephosphorylation and thereby activation of cofilin. Furthermore, in permeabilized chromaffin cells the addition of Ca2+ alone is sufficient to trigger both, regulated exocytosis and cofilin activation. This is consistent with cofilin activation being required for actin reorganization during exocytosis.