Although knowledge spillovers between firms play a critical role in the evolution of technology, we know little about such spillovers. How does knowledge flow across company boundaries? How do industry characteristics and national institutions shape knowledge diffusion? To what extent do companies direct knowledge flows? This study seeks answers to these questions by examining knowledge sharing patterns in the semiconductor industry. The research shows that public sources of technical data play a larger role in knowledge diffusion in Japan than in the United States and in semiconductors relative to steel. By understanding the mechanisms and determinants of knowledge flows, company managers and public policy makers can influence knowledge diffusion more effectively