The study of reserve risk has become an academic discipline in its own right. There are talks on the subject at most of the major P&C conferences, including this one, and several PhDs have emerged on the subject. Despite the abundance of discussion, the subject is still a bit mysterious, and can appear complex. This is not helped by the fact that there are two different measures of reserve risk: the standard actuarial view that looks over the lifetime of the liabilities, and the “one-year” view of Solvency II (the European regulatory capital regime). This presentation will compare analytical and simulation based techniques, and the “lifetime” and “one-year” views, and attempt to clarify and harmonise the approaches. The presentation will also consider risk margins in simulation based capital models under Solvency II.