How can public policy influence investment in infrastructure in network industries? Network industries rely mainly on fixed networks to deliver services, with investment being lumpy and largely irreversible. As a result, public policies – such as public provision, the introduction of competition and the regulatory environment – can potentially have an important impact on investment behaviour, with the net effect depending on the extent that policies boost socially-productive investment or reduce inefficient investment. Drawing on responses to a unique questionnaire assessing public policy in the network sectors, the information in this paper presents a systematic picture of relevant policies in place across OECD countries. Econometric analysis – both at the sectoral and firm level – finds that public policies can have significant quantitative effects. In particular, the introduction of competitive pressures through the reduction of barriers to entry and the combination of regulator independence and incentive regulation can promote investment in the sector.