Investment in network infrastructure – the energy, water, transport and telecommunication networks – which performs a vital role for the functioning of the economy, can contribute to raising growth and social welfare. But more is not always better. While the paper shows that investment in the network industries has had a positive effect over and above the addition to the capital stock, there is evidence that investment in the past has sometimes been misallocated. This paper identifies the policy framework that promotes investment that is conducive to growth and ensures the appropriate use of infrastructure. Central aspects of this framework are identified as a robust decision making process, improving the selection of investment projects, the introduction of competitive pressures through the reduction of barriers to entry and vertical separation when this is appropriate. In addition, efficient investment can be promoted by the combination of regulator independence and the application of incentive regulation.