Inventors are of key importance for the success of the research and development activities of companies. This is reflected in the high share of nearly 70% of personnel costs in total R&D expenditures. As a consequence, the determinants of productivity and mobility of inventors seems to be quite significant and should be looked at in further detail. On the one hand, an enterprise would lose a large number of possible inventions, if productive inventors leave the enterprise. On the other hand, this suggests that recruiting productive inventors should be regarded as an important personnel measure.At the company level the mobility of R&D employees is likely to be one cause of knowledge flows (spillovers) across companies. This is especially relevant for non-codified knowledge to which the public has no access. In the project we seek to identify the impact of inventor mobility on company performance. Specifically, it will be tested whether the hiring of new and mobile inventors has an impact on company productivity and profitability. It is also conceivable that specific company characteristics have an influence on the mobility of inventors. A difficult financial situation, for example, can lead to cuts in the research budget and to the quitting of inventors. In order to analyse these research questions we matched patent data from the European patent office and indicators generated from patent sources with data from the Mannheim Innovation Panel (MIP). Inaddition, we conducted a company survey on knowledge gains and losses caused by mobility of inventors. At this point of analysis the identification of single inventors with sometimes common names is of main importance. The results show that mobility is not a common and not a frequent issue in relation to the total number of inventors in Germany.