In this study, the informational efficiency of the European natural gas market is analyzed by empirically investigating price formation and arbitrage efficiency between spot and futures markets. Econometric approaches accounting for non-linearities induced by the low liquidity-framework and by technical constraints of the considered gas hubs are specified. The empirical results reveal that price discovery generally takes place on the futures market. Thus, the futures market seems to be more informationally efficient than the spot market. The theory of storage seems to hold at all hubs in the long run. There is empirical evidence of significant market frictions hampering intertemporal arbitrage. UK's NBP and Austria's CEGH seem to be the hubs at which arbitrage opportunities are exhausted most efficiently, although there is convergence in the degree of intertemporal arbitrage efficiency over time at the hubs investigated.