The Malar region is the core economic region of Sweden. Today the Malar region is the hub of different networks at both the national, the Nordic and the European level. To begin with, the Malar region and in particular its eastern part, the larger Stockholm region, plays a central role in the Swedish economy and not least in private industry in Sweden. Firstly, the region is the leading centre in Sweden for headquarter activities, including product and market development activities, of the international Swedish systems-producing companies. Secondly, the region is the leading centre in the Swedish research networks. Here we find more than 50% of the R&D activities within both the private sector and the university sector in Sweden. Thirdly, the Malar region is the most important Swedish node for the import of new ideas, knowledge, products, processes and technologies. As a matter of fact, the Malar region is the most important import node within the Nordic countries. At a European level the Malar region is one of the most important R&D regions in Europe. From a Swedish perspective it could be claimed that the Malar region is the only Swedish region with the potential to compete with the leading urban regions in Europe. It could even be maintained that if Sweden and actually the whole Nordic region is to avoid becoming a European periphery as a result of the fundamental changes taking place in Europe, the competitive power of the Malar region must be strengthened. In this paper we discuss the need of infrastructure investments within the transport sectors to strengthen the competitive power of the Malar region. We present a theory of regional development and focus in particular on the role of economic and innovation networks for regional development. The role of the infrastructure networks for the development and functioning of economic and innovation networks is discussed and a method for evaluating the productivity effects of infrastructure as well as for evaluating the profitability of investments in infrastructure is presented. Also, some empirical results for the manufacturing industry from a recent Swedish study are presented together with conjectures and conclusions regarding the need for infrastructure investments in the Malar region.