This paper studies a network provider's incentives to invest in infrastructure quality. In a simple but general framework, we investigate how various institutional settings affect investment incentives. We show that under reasonable assumptions on demand, investment incentives are smaller under vertical separation than under vertical integration. We consider two strategies for improving investment incentives under vertical separation. First, the introduction of competition for the market can sometimes improve incentives. Second, with non-linear access prices investment incentives under separation become identical to those under integration.