A method for deriving reduced dynamic models of one-dimensional distributed systems is presented. It inherits the concepts of the aggregated modeling method of Levine and Rouchon originally derived for simple staged distillation models and can be applied to both spatially discrete and continuous systems. The method is based on partitioning the system into intervals of steady-state systems, which are connected by dynamic aggregation elements. By presolving and substituting the steady-state systems, a discrete low-order dynamic model is obtained. A characteristic property of the aggregation method is that the original and the reduced model assume identical steady states. For spatially continuous systems, the method is an alternative to discretization methods like finite-difference and finite-element methods. Implementation details of the method are discussed, and the principle is illustrated on three example systems, namely a distillation column, a heat exchanger, and a fixed-bed reactor. (c) 2011 American Institute of Chemical Engineers AIChE J, 2012