We conduct an extensive empirical analysis of VIX derivative valuation models before, during and after the 2008-2009 fi nancial crisis. Since the restrictive mean reversion and heteroskedasticity features of existing models yield large distortions during the crisis, we propose generalisations with a time varying central tendency, jumps and stochastic volatility, analyse their pricing performance, and implications for term structures of VIX futures and volatility "skews". We find that a process for the log of the observed VIX combining central tendency and stochastic volatility reliably prices VIX derivatives. We also uncover a signi cant risk premium that shifts the long run volatility level.