Most studies of commodity price stabilization assume that all agents behave competitively. However, many commodities suitable for stockpiling are produced by countries with a significant share of the world market, and commodity agreements themselves often result in carterlization of the market. The paper explores the consequences of market power for the choice of storage rule and the degree of price stabilization. It finds that with linear demand, dominant producers choose more stable prices than under perfect competition and price stability increases with their market share. With constant elastic demand the competitive degree of price stabilization is achieved.