In this book, the influence of process and material parameters on the draw resonance instability in film casting and fiber drawing is investigated both for isothermal and non-isothermal conditions. Draw resonance generally occurs if the draw ratio, i.e., the ratio of outlet to inlet velocity, exceeds a critical value, and manifests itself in steady oscillations of the flow velocity and the geometric properties of the fibers and films. The focus of this book lies hereby on the determination of the critical draw ratio, as this is the parameter of most practical importance.