Empirical research shows that the relationship between proximity and knowledge cooperation assumes a linear or an inverted ‘U’ shape. This study of knowledge networks in the South Korean steel industry shows that the relationship may assume other forms. Cognitive, organizational and geographical proximity all play crucial roles in explaining the knowledge network. In the case of cognitive and geographical proximity, the relationship is linear, while in the case of organizational proximity, the relationship is wave-like, reflecting the distinctive characteristics of the country’s steel industry, which is hierarchically led by several large conglomerates.