This chapter examines how developing new technologies involves reckoning with uncertainty and distinguishes between different forms of uncertainty which are relevant to ethical discussions surrounding emerging technologies. After demonstrating the extent to which such uncertainties subvert traditional approaches to ethical reasoning, we turn our attention to the concept of risk which forms a cornerstone of ethical and practical decision-making regarding emerging technologies. Here we explore how quantitative approaches to managing risk which are common in policymaking contexts face a range of ethical limitations and examine the use of precautionary principles as an alternative method of responding to the ethical challenges surrounding technological risk.