High downside risk to income and livelihoods is part of life in developing countries. Climatic risks, economic fluctuations, and a large number of individual-specific shocks leave these households vulnerable to severe hardship. The paper explores the links between risk, vulnerability and poverty, taking a micro-level perspective. Risk does not just result in variability in living standards. There is increasing evidence that the lack of means to cope with risk and vulnerability is in itself a cause of persistent poverty and poverty traps. Risk results in strategies that avoid taking advantage of profitable but risky opportunities. Shocks destroy human, physical and social capital limiting opportunities further. The result is that risk is an important constraint on broad-based growth in living standards in many developing countries. It is a relatively ignored part when designing anti-poverty policies and efforts to attain the Millennium Development Goals. The paper discusses conceptual issues, the evidence and the policy implications.