Risk assessments are supposed to lead to decisions that provide more security. However, after a series of tragic failures such as the meltdown at the Fukushima nuclear plant, the deadly blowout on BP’s Deepwater Horizon rig, and the destruction caused to New Orleans following Hurricane Katrina, it is becoming increasingly clear that there are serious problems with our ability, or willingness, to accurately evaluate and mitigate risk. The question is, why? And what can be done about it?