A new I-D model for longitudinal dispersion is proposed as an alter-native to the Fickian-type dispersed plug-flow model. Accounting for significant features of longitudinal mixing gives rise to a quasilinear hyperbolic system of two first-order equations for the average concentration and the dispersion flux instead of one second-order parabolic equation for the average concentration. The model equations are obtained based on minor extensions of the heuristic equilibrium analysis of Taylor. A qualitative, more general derivation of the equations is given on the basis of a simple generalization of Fick’s law, taking into account the finite velocity of fluid elements. For linear problems the mean concentration and the dispersion flux obey a hyperbolic equation of the second order. The proposed hyperbolic model contains three parameters that depend only on the flow conditions, the physical proper-ties of the fluid and the geometry of the system. It effectively resolves the well-known problem of boundary conditions chat, for unidirectional flow, are formulated now only at the reactor inlet The new model eliminates the conceptual shortcomings inherent to the Fickian dispersed plug-flow model : it predicts a finite velocity of signal propagation and does not;involve backmixing in the case of unidirectional flow.