Several lines of functional neuroimaging studies have attributed a role for the insula, a critical component of the brain's emotional circuitry, in risky decision-making. However, very little evidence yet exists as to whether the insula is necessary for advantageous decision-making under risk, specifically decisions involving uncertain gains and losses. The present study uses a risky decision-making task with lesion patients and healthy controls to investigate the effects of focal insula damage on risk-taking to achieve gains and to avoid losses. Compared to healthy controls, insula lesion patients showed an altered decision-making pattern in domains involving both risky gains and risky losses. Specifically, insula damage was associated with insensitivity to differences in expected value between choice options. Additionally, patients made significantly fewer risky choices than healthy adults in the gain domain. In conjunction with earlier findings, these results suggest that risky decision-making is dependent on the integrity of a neural circuitry that includes several brain regions known to be critical for the experience and expression of emotions, namely the insula, amygdala, and ventromedial prefrontal cortex. However, each neural region seems to provide a distinct contribution to the overall process of decision-making.