This article analyses the regional determinants of manufacturing start-up ratios in Greece. Emphasis is placed on the effect of agglomeration economies, which are distinguished between urbanization and localization economies. The data refer to the establishments realized in the 51 Greek prefectures (NUTS III level) in 2005. Results indicate that negative urbanization economies prevail. Localization economies in the form of positive Marshallian and negative Jacobian externalities are observed and constitute important determinants of start-up ratios. Results regarding the effect of other factors such as expected demand and profit, cost and human resources factors are as anticipated.