This article examines the existence of threshold cointegration between futures and spot prices for the Brent petroleum market. We then estimate the asymmetric error-correction specification utilizing the Momentum Threshold Autoregressive Consistent (M-TAR-C) approach particularly proposed by Enders and Siklos (2001). We find that, for the daily data over 2 January 2001 through 15 October 2006, the petroleum futures prices are cointegrated with the spot prices. This effectively confirms the expectations hypothesis and that asymmetric adjustments for the futures basis towards the long-run value display a negative basis from the long-run equilibrium level more persistently than a positive basis from that level. The empirical result suggests that short-run arbitrages manipulating buy-long (sell-short) futures contracts be profitable when a positive basis is weakening (a negative basis is strengthening)