Recent studies have suggested that firm-specific technological competence may be diversified and internationalised. We show that increases in competence increased corporate technological diversification until the early 1970s, and then again more recently. However, a new interrelationship has now emerged between the accumulation, diversification and internationalisation of technological competence, due to the formation of internationally integrated networks within firms. The empirical analysis consists of a dynamic cross-section model applied to the corporate patenting in the US, of 166 of the largest European and US industrial firms from 1901-1995.