This paper describes work on the determination of primary commodity prices in world spot markets and in trade. Reduced-form equations for four product group price indices are estimated as functions of OECD activity, world prices, interest rates, exchange rates, oil prices, and other variables. The equations are tested for stability on their own and within the OECD INTERLINK system. The effect of exogenous shocks upon primary commodity prices is studied as well as the effect of commodity price changes upon OECD inflation and activity. The commodity price equations enter in the INTERLINK system through export unit value equations, the estimation of which is described in the paper ...