We consider factor models for interest rates and asset prices where the riskneutral dynamics of the factors process is modelled by an affine diffusion. We characterize the factors process and bond price in terms of forward-backward stochastic differential equations (FBSDEs), prove an existence and uniqueness theorem which gives the solution explicitly, and characterize the bond price as an exponential affine function of the factors in a new way. Our approach unifies the results, based on stochastic flows, of Elliott and van der Hoek (Finance Stoch 5: [511][512][513][514][515][516][517][518][519][520][521][522][523][524][525] 2001) with the approach, based on the Feynman-Kac formula, of Duffie and Kan (Math Finance 6(4): 1996), and addresses a mistake in the approach of Elliott and van der Hoek (Finance Stoch 5:511-525, 2001). We extend our results on the bond price to consider the futures and forward price of a risky asset or commodity.Keywords Affine models · Forward-backward stochastic differential equations · Stochastic flows · Bond price · Futures price · Forward price JEL Classification E43 · G12 · G13 Mathematics Subject Classification (2000) 60G35 · 60H20 · 60H30 · 91B28 · 91B70