Exocytosis is mediated by transport, docking, and fusion of secretory vesicles carrying proteins and lipids to defined areas of the plasma membrane. Through exocytosis, intracellular protein contents such as hormones and neurotransmitters can be released. Also through exocytosis, membrane proteins can be incorporated to specific domains of plasma membrane, which is crucial for cell surface expansion, cell growth, and morphogenesis. Our research aims to understand the molecular basis of polarized exocytosis. We focus on an evolutionarily conserved multiprotein complex, named the “exocyst”, which is involved in vesicle targeting and docking at specific domains of the plasma membrane. We recently found that the exocyst is a downstream effector of the Rho family of small GTPases, which are master regulators of many cellular processes such as morphogenesis and polarized cell growth. We hypothesize that Rho proteins regulate polarized exocytosis through its duo control over the vesicle transport system: the actin cytoskeleton, and the vesicle docking system: the exocyst complex. Using the budding yeast Saccharomyces cerevisiae as a model system, we are currently examining how the Rho proteins and other cell polarity regulators control the exocyst function and polarized exocytosis. Reversely, we are investigating how membrane traffic contributes to the establishment and maintenance of cell polarity. Overall, these studies may help us understand many basic biological processes such as embryogenesis, epithelial cell polarization, and neural growth cone formation.