In this paper we investigate the effects of technological and geographical proximity on knowledge flows in three economic areas: the United States, Japan, and Europe. The contribution to the existing literature is that we introduce a patent inventor approach to measuring the proximity between firms. Generally, patents are attrib- uted to the economic area where firms are located. Here, patents are described on the basis of the distribution of their inventors. The empirical results indicate that there is a statistically significant impact of technological and geographical proximity on knowledge spillovers and that these results are robust with respect to patent office data