ABSTRACT A substantial proportion of hydraulic fracture treatments are performed in formation and well completion settings conducive to the extension of multiple fractures, a process not adequately described by existing hydraulic fracture simulators. This paper introduces a procedure for the simulation of multilayer fracture treatments. The approach uses an analytical PKN fracture model to describe the behavior of each fracture and couples the behaviors using a set of constraints describing conservation of volume and continuity of pressure. The performance of the simulator is demonstrated by application to several examples.