The objective of this study was to assess the impact of variations in the area and expected yield of soybeans in the Parana state on the market prices. To determine the temporal relationships of precedence among the variables we applied the Granger causality test. The equation for growth rate of the VAR model indicate that only de expection yield and price (5% significance), both in the first time difference, were important to predict the prices behavior. For area, the constant of the model and the first time price difference are important to help explain the growth of the soybean area.