Field experiments have demonstrated that ozone (O3) pollution can reduce yields of important crop species. The assessment of the impact of O3 is facilitated by the use of a family of dose response models that covers the range of responses observed in field O3 dose response studies. The Weibull dose response model is a flexible, biologically realistic, model that has been found useful for this purpose. The purposes of the study are to discuss analyses of dose response data using the Weibull model and its extensions, to identify some of the problems inherent in the use of a nonlinear dose response model, and to show application of the model to two sets of experimental data.