Quantitative Impact Studies (QISs) have played an important role in recent years in the design and calibration of the Solvency II regime. They have provided valuable information to both CEIOPS and the European industry of the impact on firms’balance sheets of moving to a Solvency II environment. QIS4 built on the work of earlier QISs and focussed on a number of specific areas including internal models, group supervision and a new approach to the Minimum Capital Requirement (MCR).