We develop a dynamic equilibrium model of an asset market with multiple securities in which investors trade to share risks and smooth consumption over time, and investigate the empirical implications for the cross-sectional characteristics of trading volume and the dynamic volume-return relation. We extend the model to include fixed transactions costs, and when calibrated to aggregate data, the model implies realistic levels of trading volume. We also evaluate the efficacy of technical analysis in capturing the relation between prices and volume heuristically.