The paper seeks to empirically identify factors that influence the probability of being a fast-growing firm in Eastern and Western Germany. Descriptive analyses have shown that most firms experience only small positive or negative employment growth or stagnate over time. The job generation mechanism rests with a handful of firms that increase their employment significantly over time. The empirical analysis shows that the probability of being a fast-growing firm depends on different factors when separating Eastern and Western Germany as well as using different definitions of fast-growing firms. Moreover, the analysis shows that technology-intensive manufacturing branches and knowledge-based business-related services do not generate the majority of fast-growing firms.