Start-ups are a special form of enterprise foundation with potentially positive effects on the overall economy, e.g. innovation impulses, growth and employment effects. In Austria as well as at EU level start-ups are high on the policy agenda and receive considerable media attention. Beyond this background the Austrian Institute for SME Research carried out a study to formulate a definition of start-up enterprises and to make a first estimation of the number of start-ups in Austria. Main methodological principles were literature and data analyses.