A set of model amplitudes, characterized by two functions ℎ(x) and ω(x), is given which satisfies the conditions of duality, crossing symmetry, and Regge behavior. These model amplitudes can be written as G(α(s), α(t))=∫ 01 dxℎ(x)x-α(t)[ω(x)]-α(s) and are generalizations of the beta function. The model has resonances of zero width, like Veneziano's model. We prove that, under certain conditions, the model amplitude has Regge behavior as s→∞ with arg (-s) < π and t fixed, and that it dies exponentially as s→∞ with 0 < rg (s)