The effect of crude oil prices on the economic activity of countries has been considered for decades. In this period of time, the empirical link between oil price and economic activity has been continuously investigated, but the measured results have shown different results and are contradictory. Therefore, the present study aims to investigate the effect of crude oil prices on the set of economic activities in selected OPEC countries in the period 2000 to 2019. This research uses the panel data method and the system of simultaneous equations approach by the three-stage least squares (3SLS) method. The results obtained from the estimation of the considered models indicate a positive and significant effect of crude oil price on the consumer price index and liquidity volume, respectively, at the rate of 221/0 and 200/1. Also, the results indicating the negative and significant effect of crude oil price on exchange rate and interest rate are -195/0 and -175/0, respectively
