In this paper I use quarterly and monthly data from 1994 to 2014 to test if OPEC acts as a cartel, and therefore, it affects oil prices through members' coordination. I use Engle and Granger two-step approach, Johansen cointegration test and Autoregressive Distributed Lag (ARDL) bounds testing approach of cointegration to examine the long-run relation between OPEC production and each member's production as an evidence of coordination. Besides, I apply Granger causality and Toda and Yamamoto tests to check the direction of causality between the OPEC production and oil prices (U.K. Brent and Dubai Fateh). The findings show no evidence of cointegration between the production of the members and that of OPEC, indicating no cartel behavior exists. Moreover, the results show that OPEC production does not cause oil prices; rather it is the other way around. (C) 2016 Elsevier Ltd. All rights reserved.