This paper compares the volatility of spot prices (dealership market) with that of futures prices (auction market) to test the implications of different trading mechanisms for the volatility of prices. First, a natural estimator of the volatility is sued. Using the intraday data of the major Market Index and its futures prices, we show that the volatility of opening prices is higher than that of closing prices not only in the spot market but in the futures market, and that the intraday volatility patterns are U-shaped in both markets. Of particular interest is that futures prices do not appear to be as volatile as spot prices when the natural estimator of volatility is used, to the contrary of the conventional wisdom. We argue that the different volatility patterns during the day are not necessarily due to the different trading mechanisms, auction market versus dealership market. Instead, after developing a simple theoretical model of speculative prices, we show that at least part of the different volatility patterns during the day may be attributable to speculative behavior of investors based on heterogeneous information. In addition, we further investigate the volatilities of spot and futures prices using a temporal estimator of price volatility as an alternative to the natural estimator. Based on the temporal estimator, we cannot find any systematic pattern of volatilities during the day in both spot and futures markets, and that futures prices appear to be more volatile than spot prices in terms of how quickly the price moves beyond a given unit price level, but not in terms of how much the price changes during a given unit time interval. Some policy implications are also discussed.