We investigate regional differences in the effect of new business formation on employment growth in West Germany. We find an inverse Ushaped relationship between the level of start-up activity and employment change. The main variables that shape the employment effects of new businesses in a region are population density, the share of medium-skilled workers, the amount of innovation activities as measured by the proportion of research and development (R&D) employees, and an entrepreneurial character of the regional technological regime. In contrast, a high share of small-business employment has a negative influence on the employment effect of start-ups. Other indicators for education, innovation activity, and labor productivity do not prove to be statistically significant.1 Aims and scope 1 Recent empirical research strongly indicates that the effect of new business formation on economic development is of a long-term nature.2 It is found that start-up rates may have a statistically significant impact on growth for a period of up to 10 years (for an overview, see Fritsch 2008). Over this time span, the effect of start-ups on growth shows considerable variation that is in most cases (countries or regions) characterized by a wave-like pattern (see Sect. 2 for details). This wave-like pattern reveals that new businesses have a positive impact on economic development in the first 1 or 2 years after formation, but that the effect then declines and, in many cases, becomes negative. In many regions, the effect becomes positive again after about 5 years, and then A. Schroeter e-mail: alexandra.schroeter@uni-jena.de 1 We are indebted to Oliver Falck (CES-ifo, Munich), Stephan Heblich (MPI, Jena), Antonio Garcia-Tabuenca (University of Alcala, Madrid), and two anonymous referees for their helpful comments on an earlier version of this manuscript. Oliver Falck also provided very valuable advice on econometric issues.