We investigate the informational role of volume and its applicability for technical analysis. We develop a new equilibrium model in which aggregate supply is fixed and traders receive signals with differing quality. We show that volume provides information on information quality that cannot be deduced from the price statistic. We show how volume, information precision, and price movements relate, and demonstrate how sequences of volume and prices can be informative. We also show that traders who use information contained in market statistics do better than traders who do not. Technical analysis thus arises as a natural component of the agents' learning process.