Changes in maize price levels and variability in Ghana are investigated. A model of wholesale price determination is reviewed in which grain stocks are held for speculative storage as well as export to neighboring countries in the Sahel. To test the model, an Autoregressive Conditionally Heteroskedastic (ARCH) regression is applied to monthly maize data for two markets over the period 1978–93. The regression is used to measure changes in maize price volatility in Ghana, and to infer the importance of past prices, domestic and regional production, and commodity storage and trade in explaining these changes. Copyright 1996, Oxford University Press.