his paper presents a case study of how GfK NOP is moving one of the UK's major market measurement studies online. In this case study we share our learning and illustrate, with empirical data, the limits and possibilities that panel-based research offers in this most demanding arena for online research. Our conclusion is that, in this instance, it is inappropriate to replace the traditional face-to-face methodology with a wholly online solution, but that, instead, a multi-modal approach that combines face-to-face with online interviewing is the way forward.