I link an asset's risk premium to two characteristics of its underlying cash flow: covariance and duration. Using empirically novel estimates of both cash flow characteristics based exclusively on accounting earnings and aggregate consumption data, I examine their dynamic interaction in a two-factor cash flow model and find that they are able to explain up to 82% of the cross-sectional variation in the average returns on size, book-to-market, and long-term reversal-sorted portfolios for the period 1964 to 2002. This finding highlights the importance of fundamental cash flow characteristics in determining the risk exposure of an asset.