We study the effect of the tie strength of inter-firm r&d partnerships on the innovation performance of companies in four high-tech sectors (pharmaceuticals, computers, semi-conductors and telecom). Returning to granovetter's (1973 granovetter, m. S. 1973. The strength of weak ties. American journal of sociology, 78: 1360–80. [crossref], [web of science ®], , [google scholar]) seminal contribution, tie strength is analysed through a broad multi-dimensional perspective. We find that inter-firm r&d network ties that are stronger in terms of their extent (measured by the length and multitude of r&d partnerships) and weaker in terms of their depth (the degree of cooperation and the similarity of ties of companies) improve the innovation performance of companies. Interestingly, we find strong support for the role of these r&d ties in the context of the run-of-the-mill innovation performance of companies. However, there is no support for this effect on significant innovations of companies.