In this paper we use annual data from 1970-2012 to test the effect of OPEC production on oil prices through three different data structures. We use Engle and Granger, and Johansen and Pedroni cointegration tests to study the long-run relation between OPEC production and oil pric-es, besides applying Granger causality and Toda and Yamamoto tests to check the causality between the series. The findings show that OPEC production does not manipulate oil prices at the country-by-country and pooled levels, however, the effect is confirmed for OPEC acting as a cohe￢sive entity. Moreover, the results show that OPEC production does not cause oil prices at the country-by-country and pooled levels as well.