This article develops and estimates a dynamic arbitrage-free model of the current forward curve as the sum of (i) an unconditional component, (ii) a maturity-specific component and (iii) a date-specific component. The model combines features of the Preferred Habitat model, the Expectations Hypothesis (ET) and affine yield curve models; it permits a class of low-parameter, multiple state variable dynamic models for the forward curve. We show how to construct alternative parametric examples of the three components from a sum of exponential functions, verify that the resulting forward curves satisfy the Heath-Jarrow-Morton (HJM) conditions, and derive the risk-neutral dynamics for the purpose of pricing interest rate derivatives. We select a model from alternative affine examples that are fitted to the Fama-Bliss Treasury data over an initial training period and use it to generate out-of-sample forecasts for forward rates and yields. For forecast horizons of 6 months or longer, the forecasts of this model significantly outperform those from common benchmark models. (JEL C53, E43, E47)The structure of forward rates for fixed maturity loans to begin at various dates in the future can be inferred from the prices of Treasury securities or directly observed from the extremely active Eurodollar Futures market. The constellation of these rates (or of the related yields) plays a central role in the allocation of capital. The random behavior of this ''yield curve''-or the relationship between the yields and the term to maturity-is a subject of considerable theoretical and empirical study.We would like to thank the editor, Yacine Aït-Sahalia, and two anonymous referees for their guidance. We are also grateful to Amir Yaron, Michael Brandt, Francis Diebold and seminar participants at The University of Pennsylvania, Singapore Management University, the 2005 Financial Management